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SMITHSONIAN INSTITUTION 

UNITED STATES NATIONAL MUSEUM 

Bulletin 169 



THE FORT UNION OF THE 

CRAZY MOUNTAIN FIELD, MONTANA 

AND ITS MAMMALIAN FAUNAS 



BY 



GEORGE GAYLORD SIMPSON 

American Museum of Natural History 
New York City 




UNITED STATES 

GOVERNMENT PRINTING OFFICE 

WASHINGTON : 1937 



For sale by the Superintendent of Documents, Washington, D. C. ----- Price 45 cent* 



Dedicated to the Memory of 
1866-1931 



ADVERTISEMENT 

The scientific publications of the National Museum include two 
series, known, respectively, as Proceedings and Bulletin. 

The Proceedings series, begun in 1878, is intended primarily as a 
medium for the publication of original papers, based on the collec- 
tions of the National Museum, that set forth newly acquired facts 
in biology, anthropology, and geology, with descriptions of new 
forms and revisions of hmited groups. Copies of each paper, in 
pamphlet form, are distributed as published to Ubraries and scientific 
organizations and to speciahsts and others interested in the different 
subjects. 

The dates at which these separate papers are published are recorded 
in the table of contents of each of the volumes. 

The Bulletin series, the first of which was issued in 1875, consists 
of separate publications comprising monographs of large zoological 
groups and other general systematic treatises (occasionally in several 
volumes), faunal works, reports of expeditions, catalogs of type speci- 
mens and special collections, and other material of similar nature. 
The majority of the volumes are octavo in size, but a quarto size has 
been adopted in a few instances in which large plates were regarded 
as indispensable. In the Bulletin series appear volumes under the 
heading Contributions from the United States National Herbarium, in 
octavo form, published by the National Museum since 1902, which 
contain papers relating to the botanical collections of the Museum. 

The present volume forms No. 169 of the Bulletin series. 

Alexander Wetmore, 
Assistant Secretary, Smithsonian Institution. 

Washington, D. C, June 16, 1937. 



CONTENTS 

Page 

Introduction 1 

History of this study and acknowledgments 3 

Previous work 6 

Part 1: Geology and faunas 12 

Geography 12 

Geology 14 

Stratigraphy 14 

General stratigraphic column 14 

Cretaceous-Tertiary transition 16 

Fort Union 20 

Structure 28 

Fossil localities and faunal lists 29 

General occurrence of fossil mammals 29 

The Gidley and Silberling Quarries 31 

The Scarritt Quarry 34 

Other important localities 35 

Serial list of localities 43 

Index to localities by section numbers 45 

Faunal succession and correlation 46 

Combined faunal list 46 

Faunal succession 48 

Correlation of mammalian faunas 52 

Ecology 56 

Notes on nonmammalian biota 56 

Mammalian facies 59 

The Gidley Quarry and ecological incompatibility 64 

Extent of knowledge of Middle and Upper Paleocene faunas 68 

Part 2: Classification and description of mammals 70 

Order Multituberculata Cope 70 

Affinities of the Multituberculata 71 

Methods of study 73 

Family Ptilodontidae Simpson 80 

Key to American genera of Tertiary Ptilodontidae 81 

Comparison of species 83 

Genus Plilodus Cope 84 

Genus Ectypodus Matthew and Granger 99 

Genus Pareciypodus Jepsen 102 

Genus Eucosmodon Matthew and Granger 103 

Order Insectivora Gray . 104 

Family ?Deltatheridiidae Gregory and Simpson 107 

Subfamily Didelphodontinae Matthew 107 

Genus Gelastops Simpson 107 

Family Leptictidae Gill 111 

Genus Prodiacodon Matthew 112 

Genus Leptacodon Matthew and Granger 113 

Genus Myrmecoboides Gidley 115 

T 



VI BULLETIN 169. UNITED STATES NATIONAL MUSEUM 

Part 2: Classification and description of mammals — Continued, 

Order Insectivora Gray — Continued. Page 

Family Nyctitheriidae Simpson _. 118 

Genus Stilpnodon Simpson 119 

Family Pantolestidae Cope 120 

Pantolestinae, new subfamily 121 

Genus Bessoecetor Simpson 122 

Pentacodontinae, new subfamily 123 

Genus Aphronorus Simpson 124 

Family Mixodectidae Cope 127 

Genus Eudaemonema Simpson 131 

Genus Elpidophorus Simpson 133 

?Insectivora, incertae sedis 134 

Picrodontidae, new family 134 

Genus Picrodus Douglass 135 

Family uncertain.. 139 

Genus and species undetermined 139 

Order Primates Linnaeus 141 

Family ?Anaptomorphidae Cope 142 

Genus Paromomys Gidley 148 

Genus and species undetermined 156 

Genus Palaechthon Gidley 156 

Genus Palenochtha Simpson 158 

Family Carpolestidae Simpson 161 

Genus Elphidotarsius Gidley 162 

Family Plesiadapidae Trouessart 164 

Genus Pronothodectes Gidley 165 

Genus Plesiadapis Gervais 167 

Order Taeniodonta Cope 169 

Family Stylinodontidae Marsh 169 

Subfamily Conoryctinae Matthew 169 

Genus Conorycies Cope 169 

Psittacotheriinae Matthew 169 

Genus Psittacotherium Cope 169 

Order Carnivora Vicq d'Azyr 170 

Suborder Creodonta Cope 170 

Family Arctocyonidae Murray 171 

Subfamily Arctocyoninae Giebel 173 

Genus Claenodon Scott 174 

Genus D enter ogonodon Simpson 190 

Subfamily Oxyclaeninae Matthew 192 

Genus Prothryptacodon Simpson 194 

Genus Chriacus Cope 196 

Genus Metachriacus Simpson 197 

Genus Spanoxyodon Simpson 203 

Mimotricentes, new genus 203 

Family Miacidae Cope 207 

Subfamily Viverravinae Matthew 208 

Genus Didymidis Cope 209 

Genus Iclidopappus Simpson 213 

Family Mcsonychidae Cope 216 

Genus Dissacus Cope 216 



CONTENTS Vn 

Part 2: Classification and description of mammals — Continued. Page 

Order Condylarthra Cope 216 

Family Hyopsodontidae Lydekker 224 

Subfamily Mioclaeninae Matthew 232 

Choeroclaenus, new genus 232 

Genus Ellipsodon Scott 233 

Genus lAtaletes Simpson 238 

Subfamily Hy opsodontinae Trouessart 241 

Genus Litomylus Simpson 241 

Genus Haplaletes Simpson 243 

Family Phenacodontidae Cope 245 

Genus Tetraclaenodon Scott 246 

Genus Gidleyina Simpson 250 

Family Periptychidae Cope 255 

Subfamily Anisonchinae Osbom and Earle 255 

Genus Coriphagus Douglass 257 

Genus Anisonchus Cope 262 

Order Pantodonta Cope 265 

Family Pantolambdidae Cope 269 

Genus Pantolambda Cope 269 

Pantolambda or allied genera, species undetermined 271 

Literature cited 272 

Index. 279 



ILLUSTRATIONS 



Figures 

Page 

1. Diagram showing the relative abundance of identified individuals of 

the various orders and families of mammals in the National Museum 

collection from the Gidley Quarry 60 

2. Comparison of relative abundance of families of mammals at various 

localities in the Crazy Mountain Field, Mont 60 

3. Histograms illustrating Cabrera's law as applied to the Gidley Quarry 

fauna 66 

4. Histogram of measurements of second lower molars of all Lebo speci- 

mens of Metachriacus 66 

5. Histograms of typical variates of multituberculates from the Gidley 

and Silberling Quarries 74 

6. Histogram and corresponding roughly fitted normal curve of length of 

P4 in Ptilodus montanus from the Gidley and Silberling Quarries 75 

7. Scatter diagram of length of Mi and length of P4 for all Gidley and 

Silberling Quarry specimens of multituberculates that show both 

of these measurements 75 

8. Left lower jaw of Ptilodus montanus Douglass 85 

9. Lower dentitions of Ptilodus douglassi Simpson, P. gidleyi Simpson, and 

P. sincl&iri Simpson 96 

10. Lower dentitions of Ectypodus grangeri Simpson, E. russelli Simpson, 

E. silberlingi Simpson, and Paredypodus jepseni Simpson 100 

1 1 . Part of lower incisor and fragment of jaw of Eucosmodon sparsus Simpson. 103 

12. Right lower jaw of Gelastops parens Simpson 110 

13. Right lower teeth and alveoli and right lower jaw of Gelastops parens 

Simpson 110 

14. Left lower jaw of Prodiacodon concordiarcensis Simpson 112 

15. Right lower jaw of Leptacodon ladae Simpson 113 

16. Left lower jaw of Leptacodon munusculum Simpson 113 

17. Left lower jaw of Myrmecoboides montanensis Gidley 118 

18. Right upper P^-M^ of Myrmecoboides montanensis Gidley 118 

19. Left lower jaw of Stilpnodon simplicidens Simpson 119 

20. Left lower jaw of Bessoecetor diluculi Simpson 122 

21. Left upper jaw of Bessoecetor diluculi Simpson 123 

22. Left lower jaw of Aphronorus fraudator Simpson 123 

23. Right lower jaw of Aphronorus fraudator Simpson 125 

24. Left upper jaw of Aphronorus fraudator Simpson 125 

25. Left lower jaw of Eudaemonema cuspidata Simpson 132 

26. Left upper molars of Eudaemonema cuspidata Simpson 132 

27. Left lower jaw of Elpidophorus minor Simpson 134 

28. Right lower jaw of Picrodus silberlingi Douglass 137 

29. Humerus of an unidentified fossorial mammal 140 

30. Right lower jaw of Paromomys maturus Gidley 150 

31. Left upper jaw of Paromomys malurns Gidley 150 

32. Left lower jaw of Paromomys depressidens Gidley 154 

33. Left upper molars of Palenochtha minor (Gidley) 160 

VIII 



ILLUSTRATIONS IX 

Page 

34. Upper molar of Conor y des co7nma Cope 169 

35. Histogram of length of Ma of Claenodon from the Torrejon of New 

Mexico in the American Museum 178 

36. Tentatively referred specimens of Claenodon ferox (Cope) from the 

Melville (Fort Union No. 3): Left M2, right Mi, left M2-3 and heel of 

Ml, right Mi-3, and left Mi-» 180 

37. Skull and jaws, left side, of Claenodon montanensis (Gidley) 183 

38. Skull of Claenodon montanensis (Gidley), palatal view 183 

39. Foot bones of Claenodon montanensis (Gidley) 184 

40. Left upper jaw of Claenodon silberlingi (Gidley) 186 

41. Hight lower js^yv of Claenodon latidens (Gidley) 188 

42. Left M^~^ of Claenodon vecordensis Simpson 189 

43. Left Ml of iClaenodon sp 189 

44. Right M2-3 of Deuterogonodon montanus (Gidley) 191 

45. Right lower jaw of Prothryptacodon furens Simpson 196 

46. Right lower jaw of Chriacus pugnax Simpson 196 

47. Left Mi-3 of Metachriacus punitor Simpson 198 

48. Right lower jaw of Metachriacus punitor Simpson 198 

49. Left Mi~3 of Metachriacus punitor Simpson 198 

50. Left lower jaw of Metachriacus provocator Simpson 202 

51. Left M2-3 of Metachriacus provocator Simpson 202 

52. Left M'-2 of Metachriacus provocator Simpson 202 

53. Left lower jaw of Spanoxyodon latrunculus Simpson 204 

54. Left lower jaw of Mimotricentes latidens (Gidley) 204 

55. Left lower jaw of Mimotricentes angustidens Simpson 206 

56. Left lower jaw of Didymictis microlestcs Simpson 211 

57. Left P^-M^ of Didymictis microlestes Simpson 211 

58. Left lower jaw of Didymictis tenuis Simpson 212 

59. Referred specimens of Didymictis haydenianus Cope from the Lebo: 

Left upper jaw with carnassial and right upper carnassial 213 

60. Right lower jaw of I ctidopappus mustelinus Simpson 214 

61. Left upper jaw of Ictidopappus mustelinus Simpson 214 

62. Right lower jaw of Ellipsodon aquilonius Simpson 235 

63. Left upper jaw of Ellipsodon aquilonius Simpson 235 

64. Right P4-M3 and right lower jaws of Litaletes disjunctus Simpson 240 

65. Right upper jaw of Litaletes disjunctus Simpson 240 

66. Left lower jaw of Litomylus dissentaneus Simpson 242 

67. Right M'"' of Litomylus dissentaneus Simpson 242 

68. Right lower jaw of Haplaletes disceptatrix Simpson 244 

69. Right upper jaw of Haplaletes disceptatrix Simpson 244 

70. Right lower jaw (with Mi) of Tetraclaenodon symbolicus Gidley 247 

71. Right Mi-2 and right M'^~^ of Tetraclaejiodon symbolicus Gidley 247 

72. Left upper jaw of Gidleyina montanensis (Gidley) 252 

73. Left lower jaw of f Gidleyina silberlingi (Gidley) 254 

74. Ijefi lower ]&w of f Gidleyina superior (Simpson) 255 

75. Left lower jaw of Coriphagus montanus Douglass 260 

76. Left upper jaw of Coriphagus montanus Douglass 261 

77. Right lower jaw of referred specimen of Anisonchus sectorius (Cope) 

from the Lebo 261 

78. Right upper jaw of referred specimen of Anisonchus sectorius (Cope) 

from the Lebo 261 

79. Histogram of length of Mi in Anisonchus sectorius (Cope): Torrejon 

and Lebo specimens 263 

80. Right lower jaw of Pantolambda intermedins Simpson 270 



X BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

Plates 

Pollowiag 
page 

1. Reconnaissance map of the mammal-bearing Fort Union group of the 

Crazy Mountain Field, Wheatland and Sweetgrass Counties, Mont. _ 12 

2. Bear and Lebo formations. Crazy Mountain Field, Mont 277 

3. Air views of Fort Union group. Crazy Mountain Field, Mont 277 

4. Air views of Gidley Quarry, Fort Union group, Crazy Mountain Field, 

Mont 277 

5. Air view and site of the Silberling Quarry, Fort Union group. Crazy 

Mountain Field, Mont 277 

6. Melville formation. Crazy Mountain Field, Mont 277 

7. Fort Union primates: Palaechthon alticuspis Gidley and Paromomys 

maturus Gidley, right lower jaws 277 

8. Fort Union primates: Pronothodectes matthewi Gidley and Paromomys 

maturus Gidley, left lower jaws 277 

9. Fort Union primates: Plesiadapis gidleyi (Matthew), Pronothodectes 

matthewi Gidley, Plesiadapis rex (Gidley), Palaechthon alticuspis 
Gidley, Paromomys depressidens Gidley, and undetermined species, 

dentition 277 

10. Fort Union primates: Palenochtha minor (Gidley), Elphidotarsius 

fiorencae Gidley, and Pronothodectes matthewi Gidley, lower jaws 277 



THE FORT UNION OF THE CRAZY MOUNTAIN 
FIELD, MONTANA, AND ITS MAMMALIAN 
FAUNAS 



By George Gaylord Simpson 

American Museum of Natural History, New York City 



INTRODUCTION 

This work is chiefly devoted to the description and discussion of 
a large collection of Paleocene mammals, from the Fort Union of 
central Montana, belonging to the United States National Museum. 
The first part of the memoir is geological, chiefly stratigraphic and 
paleontological. The location and general characteristics of the 
mammal-bearing area are described, followed by a resume of its 
stratigraphy and geologic ftnicture. The general areal geology is 
only briefly outhned, and details are largely confined to the beds in 
which the mammals occur. In the paleontological section, the various 
fossil localities are hsted, and the mammalian fauna of each is given, 
together with a summary of all fossil mammals found in the field. 
Faunal succession and faunal correlation, supplementing the remarks 
made in the previous section on more purely stratigraphic correlation, 
are discussed in detail. The general aspect and ecologic relation- 
ships of the mammaUan faunas are also discussed. Nonmammalian 
fossils are incidentally mentioned, without any attempt at exhaustive 
treatment. 

The second and longer part of the memoir is zoological and is 
devoted to definitions of all taxonomic groups which were originally 
described from this field or the conception of which is markedly 
affected by material from here, to discussion of the relationships 
and phylogeny of the mammals represented, and to description of 
the specimens in the coUection. 

Geology outside the area of reference and mammals other than 
those definitely identified here are mentioned only for the sake of 
comparison. 

In addition to the National Museum collection, specimens from 
this field now at Princeton University are included. Reference is 
also made to a small collection in the Carnegie Museum, but since 
this includes nothing not better represented in the National Museum 
collection, none of it is treated in detail. Some, but not all, of a 
large collection in the American Museum of Natural History from 

1 



2 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

this same field is also mentioned or discussed. In a few cases classi- 
fication has demanded some detail concerning fossils from other col- 
lections and areas, especially the San Juan Basin, in New Mexico, 
notably in deahng with the genera Claenodon and Anisonchus. 

Most of the new genera and species recognized in the course of 
this work were named, with brief diagnoses, in a preUminary note 
abstracted from the first draft of part 2 (Simpson, 1935d). These 
diagnoses are here repeated, in some cases in emended form, and ac- 
companied by the extended discussion and description omitted in the 
preliminary paper. There is included a full discussion of the fossil 
Primates, even though these have already been published in some 
detail (Gidley, 1923). 

In the course of preparation of tliis bulletin, I have had access 
to and have made constant use of a memoir on the Paleocene of the 
San Juan Basin by the late Dr. W. D. Matthew. This has now 
been published by the American Philosophical Society, but it was 
available only in manuscript throughout the course of my work. 
Reference to it is made by the citation "(Pale. Mem.)." Other 
citations are by author and year and refer to the "Literature cited" 
at the end. As far as possible without destroying the comprehensive 
and unified character of this work, I have avoided any duplication 
of material contained in Matthew's memoir. For groups that he 
also discusses I have generally omitted diagnoses and have confined 
discussion to a brief surmnary and to those pomts wherein I differ 
from him. 

Throughout this work, wherever they proved useful, statistical 
methods have been employed. These are all summed up in Fisher 
(1925) and also in a paper soon to be published (Simpson and Roe). 
The methodology is outlined here in connection with the first group 
treated, the Multituberculata. In all the statistical figures given, 
the stated error is standard, not probable. The following abbrevi- 
ations are consistently used throughout for brevity, along with the 
universally understood symbols for teeth. 

L«= Length. 
W = Width. 

N = Number of specimens in a given sample. 
R^ Range. 
M = Mean. 
o-^ Standard deviation. 
d/<r== Deviation from a specified mean, divided by the corresponding stand- 
ard deviation. 

V>=CoeflBcient of variability = --—-• 

M 

P= Probability. Mas defined 

t = A constant for comparing small samples] [by Fisher. 

2(d')'=Sura of the squares of deviations from the mean. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 3 

In the systematic zoological part of this work, it has not seemed 
necessary in each case to give the evidence or arguments for associa- 
tions of upper and lower dentitions. With very few exceptions these 
collocations are not based on actual association of upper and lower 
jaw remains of one individual, which is very rare in this field. It is 
based rather on occlusion, occurrence at the same locaUties, relative 
abundance, comparison with related forms from other fields, and 
similar indirect but usually conclusive criteria. In the few cases 
where there is any serious doubt about the association, this fact is 
mentioned. 

This manuscript was completed on March 15, 1936. Slight changes 
have since been introduced, but no later general revision has been 
made, and with few exceptions statements made are to be taken as 
of that date. 

HISTORY OF THIS STUDY AND ACKNOWLEDGMENTS 

Work for this memoir was started in 1908, when Dr. T. W. Stanton 
commissioned Albert C. Silberling to collect Fort Union fossils for 
the United States Geological Survey and the United States National 
Museum. In 1909 Dr. J. W. Gidley visited the field, where he di- 
rected and planned further work by Silberling, and he also then under- 
took the laboratory and office work on the collection. In view of 
the extremely fragmentary and few fossil mammals that had been 
collected in the Fort Union up to 1908 and the general scarcity of 
mammals of comparable age from any formation, the magnitude to 
which this work would grow could not have been anticipated when 
it was started. In 1911, when Mr. Silberling finished his most inten- 
sive work on tliis collection (to which he also added periodically until 
1932), he had brought together one of the largest collections of Paleo- 
cene mammals ever made. Furthermore, this collection consisted 
almxost entirely of new species, more than half the genera were new, 
and it greatly extended morphological and distributional knowledge 
of the families and orders represented. The collection represented, 
potentially, the greatest single contribution to knowledge of early 
mammals that had ever been made. 

The very magnitude of the results achieved was embarrassing. 
All these hundreds of specimens had to be prepared, the majority 
of them by tediously worldng oft' the matrix grain by grain under a 
microscope. Concurrently wdth many other duties, this was undertaken 
by Dr. Gidley, and it occupied much of his time over a period of 12 
years. Then the identification of the material presented great diffi- 
culties, as it must in any Paleocene collection, for on one hand all the 
genera and species are clearly variable and on the other the really 
significant characters are often in such small details that it may be 
diflficult to distinguish forms properly classified in different orders. 



4 BULLETIN 169, UNITED STATES NATIONAL. MUSEUM 

These difficulties were enhanced by the fact that the most pertinent 
comparative material was in another institution and that Dr. Gidley's 
other duties did not permit his spending the months, or even years, 
of comparative study necessary under these circumstances, except by 
short visits or the loan of a few specimens as opportunity presented. 

In spite of the- really tremendous amount of work that he had 
accomplished on the collection, Dr. Gidley was able to complete only 
a relatively small part of the final preparation and publication of 
manuscript before his death on September 26, 1931. Up to the end, 
he looked forward to the completion of the work, and remarked, in 
conversation, that the collection was the most important ever in his 
hands and that its publication would be his greatest contribution to 
science and his most enduring monument. This it is, despite the 
fact that he was not spared to complete it with his own hands. 

In 1932, Dr. Alexander Wetmore and C. W. Gilmore invited me to 
undertake the completion of this study. The officers of the American 
Museum of Natural History permitted the use of my time, as a coop- 
erative undertaking with the United States National Museum. The 
whole collection was shipped to New York, where it could be studied 
under the best possible circumstances and compared at first hand wdth 
almost all the other types of American Paleocene mammals. Knowl- 
edge of the field, and further accessions to the collections, were made 
possible by work with Mr. Silberling in Montana for the National 
Museum in 1932 and for the American Museum in 1935. 

The great extent of Dr. Gidley's contribution to this work should 
be explicitly stated.^ In the first place, the existence of this splendid 
collection is in large part due to him. He collected some of the best 
material, and he directed and encouraged the collection of most of it. 
Second, he prepared and cataloged the whole collection so that it 
came to me in almost perfect condition for immediate study. Third, 
he prepared and published four preliminary papers (as fisted in the 
bibfiography and discussed in the proper places in the text). It is 
inevitable that some differences in point of view and more particularly 
the lapse of time make complete agreement impossible, but his pre- 
liminary work greatly facifitated study of the groups involved. 
Fourth, a number of unpublished iUustrations had been prepared 
under Dr. Gidley's direction, and most of them appear in this publi- 
cation. Finally, he left a few notes on the unpublished parts of the 
collection. 

There is reason to believe that Dr. Gidley had the major outlines 
of the classification of the collection, and probably also many of its 
details, well in mind. This preliminary orientation is one of the long- 
est and most difficult parts of research, but unfortunately Dr. Gidley 
did not find it necessaiy for his own use to reduce it to writing and 

> For a review of Dr. Gidley's life and work see Lull (1932), 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 5 

could not foresee how important this would have been for his suc- 
cessors. The available notes are thus fewer and less useful than was 
anticipated. Specifically, they are as follows: 

1. A field notebook containing a fist of 43 specimens collected by 
Gidley, with locahty, horizon, and date, but no other data. 

2. Illustrations and proofs of his paper on the Primates, with no 
unpublished data. 

3. Notes on multituberculates and claenodonts, with no unpublished 
observations. 

4. Twenty-seven pages of notes and of manuscript in various stages 
of preparation, with considerable duplication and difterent drafts of 
treatments of the same subject. These, the only unpublished original 
observations left by Dr. Gidley, include brief prehminary diagnoses of 
three new species of Tetraclaenodon, one of Protogonodon, one of Mio- 
claenus, one of Tricentes, one of Mixodectes, and one of a genus probably 
considered as new but not named or defined, and also a sketch diag- 
nosis of a new genus and species of phenacodonts (here called Gidleyina 
montanensis) . 

As far as they can be deduced from these notes, I have mentioned 
Dr. Gidley's opinions in the present text. In some cases they warrant 
detailed discussion and quotation. In others, his notes were clearly 
of the most preliminary sort and would surely have been modified 
before publication, and in these cases it has seemed unjust to do more 
than mention them briefly. As regards the recognition of species, 
I first studied the collection independently and then ascertained 
whether any new species (or genera) recognized by me were antici- 
pated in Dr. Gidley's notes. If they were, I credited them to Gidley, 
ex ms}, and quoted sufficient of his diagnosis to estabfish his author- 
ship. The species so recognized are Deuterogonodon montanus, Mimo- 
tricentes latidens, Tetraclaenodon symbolicus, and Gidleyina montanen- 
sis. Dr. Gidley's notes also include diagnosis of the genus Gidleyina 
but under a preoccupied name. 

Some other new forms are recognized in the notes, but without a 
name or without a diagnosis or definite indication, so that Dr. Gidley 
could not technically be established as their author, but his recognition 
of them is mentioned. In a few cases I have been unable to agree that 
a form tentatively designated as new by Dr. Gidley is so, and then have 
pointed out this fact but have omitted his names in order not to create 
useless synonymy. 

None of Dr. Gidley's notes were in such shape that it would have 
been just to him to publish them without revision, and in any event 
only a small part of this memoir is affected by his unpubfished notes. 

> The International Rules of Zoological Nomenclature, Article 21, state that the author of a scientific name 
is he who first publishes it with a valid definition "unless it is clear from the contents of the publication that 
some other person is responsible for said name and its Indication, definition, or description." This validates 
Gidley's authorship of these species published by me. 



6 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

That this work has been ^vTitten at all is largely due to Dr. Gidley, but 
he is not responsible for its errors or for any matter in it not expHcitly 
stated to be his. 

It is further desired to acknowledge how much this work owes to 
Albert C. Silberling, whose contributions to it go far beyond those 
usual from a collector. He discovered most of the fossil localities, 
including all those of real importance, and made far the greatest part 
of the collection, \vdth skill, persistence, and devotion that cannot be 
too highly praised. He established a system of field records of the 
greatest accuracy, used throughout this pubhcation. Even beyond 
this he so thoroughly examined the field and so carefully studied and 
correctly interpreted its geology that much of what is here written 
about it, and of what has appeared in publications by others, is merely 
reducing to writing observations made by or with him. He is thus in a 
sense an author and authority of the geologic part of this work, 
although he has not actually written any of it and is not responsible for 
misinterpretation of his views or observations. Aside from the long 
periods when he was definitely employed as a collector, Mr. Silberling 
has spent every spare moment for the past 35 years worldng in this 
field, and this memoir is in a real sense the outcome of this lifetime 
vocation and avocation. 

The following illustrations were drawn by Rudolph Weber under 
Dr. Gidley's direction: Figures 22, 30-34, 37-41, 446 and b', 59, 63a, 
71a and a', 72, 736, 80.^ The other dramngs were made by Sydney 
Prentice, under my direction. The accompanying map is based on 
field work by Silberling and me and was drawn by John C. Germann. 
The field photographs were taken by me. 

The late Prof. W. J. Sinclair, of Princeton University, lent and per- 
mitted the description of the specimens collected for that institution 
by Douglass and by parties under Farr. Dr. G. L. Jepsen has facili- 
tated comparisons with specimens collected under his leadership for 
Princeton in the Fort Union of Wyoming. The Carnegie Museum, 
through J. J. Burke, lent material in their collection from this field. 
I am much indebted to these institutions and colleagues, as well as to 
officials of the United States National Museum, particularly Dr. Wet- 
more and Mr. Gilmore, for their support of the work and constant aid 
and encouragement, and of the American Museum of Natural History 
for the time and facilities provided. 

PREVIOUS WORK 

Discovery of Paleocene* mammals lagged behind that of typical 
faunas of any later epoch, or even of the Mesozoic. This slowness of 
discovery and the factors of scarcity of fossils and difficulties of study 

' In a few cases Prentice has modified these drawings slightly. 

* "Paleocene" is granted to be an epoch of the Tertiary, including post-Lance or post-Danian and pre- 
Qray Bull or pre-Sparnacian time. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 7 

to which it was due have made the subject of Paleocene mammals an 
obscure one, generally avoided, but they have also made it a particu- 
larly fruitful field for research in recent years. 

The first Paleocene mammalian fauna to be discovered was that of 
the Thanetian, or particularly of its subdivision the Cernaysian, in 
France. Arctocyon primaevus was described by Blainville in 1841, but 
knowledge of the fauna really dates from Lemoine's pubhcations 
beginning in 1878. It has only recently been revised and placed on a 
satisfactory basis by Teilhard (1916, 1921). 

The American Puerco formation of New Mexico was named in 
1875 but yielded no mammals until 1881, when the famous collector 
David Baldwin began a long collecting campaign there for Cope. This 
work has been followed, since 1892, by a series of expeditions to this 
field under Wortman, Granger, Sinclair, Simpson, and others for the 
American Museum of Natural History, which also acquired the Cope- 
Baldwin collection. This stratigraphic sequence in the San Juan 
Basin of New Mexico has become the standard of comparison for the 
Paleocene of the world, and its faunas are far the best known and 
represented by the most nearly perfect specimens (although in variety 
they do not exceed those to be described in tliis memoir). They have 
been described by Cope, Osbom, Earle, Wortman, Matthew, Granger, 
Simpson, and others and are thoroughly revised in a memoir by 
Matthew (Pale. Mem.), published while this bulletin was in press. 
Three quite distinct formations and faunas have been recognized, 
Puerco, Torrejon, and Tiffany, the first two each with two well-marked 
separate faunal zones of different facies but nearly the same age. 

The Fort Union group was originally defined by Meek and Hayden 
(1861) as occupying ''the country around Fort Union,^ extending north 
into the British possessions to unknown distances; also southward to 
Fort Clark. . . , Seen under the White River group on North Platte 
River above Fort Laramie. Also on west side of the Wind River 
Mountains. . . . and also occupying extensive areas of country in 
Nebraska . . . and beneath the White River group at several distant 
locahties." Although the designation of the type locality leaves no 
doubt as to the inclusion of certain strata in the group or as to its 
general position in the scale, the name has been used in man}^ different 
ways, and in keeping with the spirit of the original description it has 
been applied to any or all strata at about tliis part of the geologic 
section, that is, in what we now call Paleocene, over a very large area 
in the Northwest. Thanks to this widespread occurrence or use of the 
name, and to the economic value of these rocks, especially as a coal- 
bearing series, few geologic formations have been more intensively and 
extensively studied. No general review of this work is here attempted _ 

* Near the present site of Buford, N. Dak. 
119212—37 -2 



8 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

(see resume and references in Thorn and Dobbin, 1924) aside from the 
Crazy Mountain area and briefer mention of mammal discoveries 
elsewhere. 

The earliest geological work in the particular area here under dis- 
cussion appears to be that of W. H. Weed. In 1893 he mentioned the 
presence of about 4,000 feet of Fort Union sediments overlying his 
Livingston formation east of the Crazy Mountains. In the Livingston 
(Weed, 1894) and Little Belt Mountains (Weed, 1899) fohos, he in- 
cluded the extreme western part of this area and referred to the 
presence of Fort Union here but mapped it all as Livingston. In an 
article on the Fort Union (Weed, 1896) he also discussed the Fort 
Union area in a general way and gave a section of part of these and of 
lower beds along Lebo Creek. 

The first more detailed consideration of this area and the first ade- 
quate reference to its more important northeastern part was by Earl 
Douglass. In 1900 he worked here, principally in the Cretaceous but 
also in the Fort Union, where he collected leaves and invertebrates. 
In 1901 a Princeton University expedition was sent out under Dr. 
M. S. Farr, and Douglass accompanied this party and also continued 
work after they had left. The Princeton party traversed the Fort 
Union exposures, but most of theu* work of that season was in the 
Cretaceous. In August 1901, Douglass found the first mammals in 
this field, and the first ever discovered in the Fort Union, at two 
locahties (5 and 6 of the lists given on a later page) near the northern 
end of Bear Butte. Although fragmentary and few, these sufficed to 
show the equivalence of these beds to the Torrejon of New Mexico 
(Douglass, 1902a). Douglass soon pubhshed detailed descriptions of 
the mammals and a discussion of the geology of the whole area (Doug- 
lass, 1902b). The Princeton party was also accompanied by Albert 
Silberling, then a boy of 16, who was destined to play the major role 
in the development of this field. 

Princeton field parties, also under Dr. Farr and accompanied by 
Silberling, revisited the area in 1902 and 1903, and they then examined 
the Fort Union in more detail and found fossil mammals at a number 
of scattered localities and at widely different levels, from near the base 
of the formation to about 4,350 feet above the base and from the 
northeastern part of the field to the vicinity of Cayuse Butte, near the 
western margin of the principal mammal-bearing area. The fossils 
collected and observations made in 1902 and 1903 have never been 
published. 

In 1905 Douglass made a long reconnaissance through Montana, 
and in the course of this he went northward from Bigtimber to Cayuse 
(or Melville) Butte. He noted the presence of the Fort Union over 
much of this traverse but did not add significantly to exact knowledge 
of the field. Apparently he had not been informed of the unpubfished 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 9 

discoveries of 1902 and 1903 on and around Cayuse Butte, and he 
found no mammals on his brief visit. His account of this trip (Doug- 
lass, 1909) includes a resume of the geology of the area, involving also 
bis observations in 1900 and 1901. 

In the meantime Silberling had continued prospecting the field and 
had located the two richest known deposits, later developed as the 
Silberhng and Gidley Quarries. He was for a tim^e associated with the 
Carnegie Museum, to which Douglass had now also gone, and he sent 
in to it a small but important collection, principally from the Silberling 
Quarry. This was described by Douglass a few years later (Douglass, 
1908) and was the basis of the first exact definition of mammals from 
this field, including the types of Ptilodus montanus, Picrodus silber- 
lingi, Coriphagus montanus, and Alegopterna minuta,^ as well as many 
less exactly identifiable specimens. 

In 1907 (see Stone, 1909) R. W. Stone worked in the northern part 
of this area for the United States Geological Survey, and in 1908 
W. R. Calvert worked south of the area. They connected their ob- 
servations west of the Crazy Mountains, and in 1909 also by recon- 
naissance east of the mountains and later published an important 
discussion of the Fort Union here and of its relations to the Livingston, 
applying the name Lebo to the lower part of the Fort Union (Stone 
and Calvert, 1910). 

In 1908 Dr. T. W. Stanton visited the field, where he was accom- 
panied by Silberling, who had in the meantime left the Carnegie 
Museum and started ranching in this area. They made detailed 
observations, including a section of the Lebo which I give on a later 
page, and Silberling was employed under Stanton's direction to collect 
for the United States Geological Survey and National Museum 
(Stanton, 1909). Ejiowlton had taken some interest in observations 
here, principally in connection with his placing of the Hell Creek and 
synchronous beds in the "Lower Fort Union" (see Knovvlton, 1909), 
a view now universally abandoned and requiring no consideration 
here. In 1909, Stanton, Stone, Calvert, Knowlton, and M. R. 
Campbell briefly visited the area again to check certain critical 
locaHties, the results of their observations being principally given by 
Stone and Calvert (1910). Stanton (1914) and Knowlton (1914) 
later returned to their argument regarding the Cretaceous-Tertiary 
boundary, but with only incidental reference to this area. 

Silberling continued the collecting begun in 1908 and spent much 
time in 1909, 1910, and 1911 collecting for the National Museum. 
It was in these years that he obtained most of the specimens described 
in this work. A few specimens collected in later years were also 
acquired by the National Museum, and Silberling has continually 
spent much time in the field, even when not commissioned by any 

9 Which is, however, invalid. 



10 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

particular institution. In 1908 he had worked principally in the 
Silberling Quarry. In 1909 Gidley visited the field and then opened 
the Gidley Quarry at a site, Loc. 4, previously discovered by Silberling. 
Gidley himself collected many fine specimens here, and the work was 
continued by Silberling in 1909-11, and later, along with repeated 
prospecting of surface localities. In 1911 Gidley made another visit 
to the field.^ 

In 1909 Gidley described the splendid skull, jaws, and partial skele- 
ton of Ptilodus that had been found in 1908 by Silberiing in the Silber- 
ling Quarry. This is still the best multituberculate specimen in any 
museum, and the best single mammal specimen ever found in this 
field. Gidley continued the preparation of the collection, work done 
entirely by himself, as time and other duties permitted. Tliis was 
completed in 1920. In the meantime two preliminary papers had been 
pubhshed, one on Myrmecoboides (Gidley, 1915) and one on the clae- 
nodonts (Gidley, 1919). After the whole collection was prepared he 
began monographing it, but only the section on the Primates (Gidley, 
1923) was completed or published. The extent of his unpubUshed 
work has already been noted. 

In 1930 Silberling made a renewed examination of the field and also 
reopened the Gidley Quarry and made a collection that was purchased 
by the American Museum. In 1932, under the auspices of the Na- 
tional Museum (with the donation of my services by the American 
Museum), Silberling and I went over the whole area and adjacent 
regions, with the present work in mind. We then made the map 
(pi. 1) that accompanies this memoir and also made detailed strati- 
graphic observations. A small amount of material was collected, 
incidental to our visits to all the fossil localities, but no intensive 
collecting or quarrying was undertaken. 

In 1935 the Third Scarritt Expedition of the American Museum, 
consisting of Mr. Silberling, a camp man, and me for the entire season, 
and Mr. and Mrs. Fenley Hunter, Dr. Walter Granger, and Albert 
Thomson for shorter periods, spent four months in tliis field, pros- 
pecting most of the surface localities, reopening the Gidley and Silber- 
hng Quarries, and developing a new quarry, named the Scarritt 
Quarry. The resulting collection, about equal in size to that here 
described, is in the American Museum. The material from the Scar- 
ritt Quarry has been described (Simpson, 1936b), and the results are 
here included in the general sections but not in the detailed descrip- 
tions. The surface material, wliich is relatively abundant and im- 
portant but does not include any species not also present in the 
National Museum collection, has also been identified and is mentioned 
where apropos in the present work. The very large Gidley Quarry 

' Gidley's statement (1923, p. 1) that he visited the field in 1008 and 1909 is probably a misprint, for it is 
contrary to Silberling's memory and to letters and other records that seem to show that his visits were in 
1909 and 1911. 



FOKT UNION OF CRAZY MOUNTAIN FIELD, MONT. H 

collection, and the few specimens from the Silberling Quarry, in the 
American Museum are not yet studied and do not enter into this 
study. For the most part they duplicate the collection described 
here. 

Of other mammal discoveries in the Fort Union, the first of any im- 
portance was made by J. F. Lobdell in 1926 in a coal mine at Bear 
Creek, Mont. Collections were later made here for the Carnegie 
Museum and the American Museum and have been described by me 
(Simpson, 1928a, 1929a, b). The small but interesting fauna is of 
Upper Paleocene age, about equivalent to the Tiffany. 

Discoveries in northern Wyoming, west of the Bighoi-n Mountains, 
have been of outstanding value. Sinclair and Granger (1911, 1912; 
also Granger, 1914) had found a fauna of Paleocene aspect here in 
beds which had previously been considered to be true Eocene and 
which they named Clark Fork. In 1927-29, Dr. G. L. Jepsen, work- 
ing for Princeton University, found three distinct faunal horizons in 
(nominal) Fort Union strata beneath the Clark Fork in this area. 
He has shown that these correspond in age to the Puerco, Torrejon, 
and Tiffany, and hence has for the first time established a definite 
sequence of four distinguishable Paleocene mammahan faunas in a 
single continuous stratigraphic section (Jepsen, 1930). The faunas 
so far described are small but typical. Subsequent collecting under 
Jepsen at the same localities has yielded much more and better 
material, but the results have not yet been published. 

Sporadic discoveries of one or two specimens have been made at a 
few other Fort Union localities, but none is of much importance. 
The type of Titanoides immaevus came from near the type locality of 
the group, Buford, N. Dak. (Gidley, 1917). Typically Middle 
Paleocene forms, Tetraclaenodon and Pantolamhda, were found in 
Billings County, N. Dak. (Lloyd and Hares, 1915). In Fort Union 
or Kingsbury beds of the Bighorns a jaw identified by Gidley as 
Tricentes was found (Stanton, 1909, p. 268). Eocene fossils were 
found in supposed Fort Union beds in the Powder Eiver Basin (Wege- 
mann, 1917). The last-mentioned fossils, and perhaps that from the 
Kingsbury, are not really from the Paleocene, or from true Fort 
Union. 

The Paskapoo of Alberta, which may be considered in a general 
way a northern extension or equivalent of at least the upper part of 
the Fort Union, has yielded a few mammals, the first found by Brown 
in 1910 (Simpson, 1927), with later discoveries mostly by Russell 
(1926, 1929, 1932), all extremely fragmentary. Recently Patterson, 
working for the Field Museum of Natural History, collected fine' skele- 
tons of Barylambda, an ally of Titanoides, at an Upper Paleocene level 
in the Plateau Valley formation of western Colorado (Patterson, 1933, 
1934, 1935, 1937). 



PART 1: GEOLOGY AND FAUNAS 

GEOGRAPHY 

The region here primarily considered is comprised in Tps. 3-6 N. 
and Rs. 13-16 E. (Montana principal meridian), an area of about 575 
square miles. It is approximately included in latitude 45°55' to 46°20' 
N., longitude 109°40' to 110° 10' W., and is in central Montana, 
Tps. 3-5 N. in Sweetgrass County and T. 6 N. in Wheatland County, 
The principal commercial center is Hariowton, seat of Wheatland 
County, 8 miles due north of the designated area. This town, popula- 
tion about 1,500, is on the north side of the Musselshell River and is a 
division point on the main line of the Chicago, Milwaukee, St. Paul, 
and Pacific Railroad. About an equal distance south of the area is 
Bigtimber, population 1,200, on the south bank of the Yellowstone 
River. The only settlement in the limited region here primarily 
treated is Melville, an old town once of some importance but now 
reduced to little more than a post office and crossroads store. It is in 
sees. 11 and 14, T. 4 N., R. 14 E. 

There are main east-west motor highways and railroads in the 
Musselshell and Yellowstone Valleys, north and south of this area, 
but just here east and v/est through travel is blocked by the impassable 
mountains immediately to the west. There is, however, a secondary 
north-south highway from Hariowton to Bigtimber through the area, 
and this is now being improved and graveled (1935). There are 
several county roads, graded but unsurfaced, as shown on the map, 
and also many private roads and wagon trails, which permit approach 
to within a mile or less of any point in the field. 

Much of the land has been plowed for dry-land wheat raising, but 
a great deal of it was not suitable for this purpose and so most of the 
wheat farms have been abandoned. A little wheat and some hay or 
alfalfa are still raised, but most of the region is given over to grazing, 
mainly as winter range for sheep and some cattle. The population is 
sparse and in recent years has not been prosperous. There are a few 
dude ranches in and near the mountains in the western part of the 
field. There are no known mineral resources. 

Topographically the area lies immediately east of the Crazy Moun- 
tains, a very rugged and beautiful isolated range 25 or 30 miles long, 
north to south, and 10 to 15 miles in width, rising to 11,178 feet in 
Crazy Peak. The area specifically treated extends from the foothills 
of the mountains eastward about 25 miles. The divide between the 
Musselshell and Yellowstone Rivers runs through the field. The 
northern part is drained mostly by Fish Creek, here running eastward, 
12 



T.6N 



T.5N 




T.4N 



RECONNAISSANCE MAP OF THE MAMMAL BEARIN5 
FORT UNION GROUP 

OF THE 

CRAZY MOUNTAIN FIELD 

WHEATLAND AND SWEETGRASS COUNTIES 

MONTANA 



^FORMATION CONTACTS 



FORT UKION OF CRAZY MOUNTA.IN FIELD, MONT. 13 

and its southern part mostly by Sweetgrass and Otter Creeks and 
their tributaries, here running mainly southeastward. The extreme 
northwestern part is drained by American Fork and Lebo Creeks, 
tributaries of the Musselshell, and the extreme southwestern part by 
Bigtimber Creek, tributary to the Yellowstone. Lebo and Fish 
Creeks rise in this area and carry little water in ordinary weather, 
while the other streams mentioned rise in the mountains and have 
larger and more nearly permanent flow. 

Apart from the actual mountain area and its flanking zone of 
pediments, moraines, and outwash, here poorly developed, this region 
is a hilly one v/ith mature topography almost entirely determined by 
the hardness and structure of the underlying rocks. The harder 
sandstones form ridges and scarps, and the softer beds are eroded into 
valleys or flats. The most striking elevations in the northeastern 
part of the field, lilce Bear Butte and Lion Butte, are sandstone- 
capped erosion forms. Cayuse Butte, a prominent but relatively low 
and irregular mass, and Porcupine Butte, the most prominent eleva- 
tion outside the mountains, also are supported by intrusive igneous 
rocks (as are the mountains). The southern part of the field is hilly 
but has no prominent topographic features. There are three small lakes 
in the area, Lebo Lake in the northwest and Lakes Adam and Wal- 
voord (more generally known as the Glass Lindsay Lakes) in the 
southeast, all artificial and developed for irrigation. 

The highest point outside the mountains is Porcupme Butte, 6,970 
feet, and the lowest is on Fish Creek where it leaves this area, about 
4,000 feet. 

Climate and vegetation vary from mountain to high-plains types. 
The mountain flanks have forest of lodgepole pine and other conifers, 
with aspens along the streams and some colorful meadows, while the 
main part of the field is very sparsely timbered, with evergreens on the 
higher sandstone ridges and cottonwoods in wet valley bottoms. 
The broad intervening areas, except for the relatively small uTigated 
patches, are characterized by sagebrush, pricklypears, small yuccas, 
and grass. Abandoned plowed land is taken over by weeds, especially 
Russian thistles. In spite of the rather sparse nature of the vegeta- 
tion, almost the entire area is sodded over. Shale exposures are small 
and relatively few, and there are no badlands. 

The topography along the northern edge of the area (beyond the 
Fort Union exposures) is very different, for here there are large, well- 
developed, high, gravel-covered terraces cutting across the tilted 
Cretaceous beds without regard for their hardness. s?.,| 

This general Fort Union area has received various designations, 
such as "Fish Creek", "Bear Butte", "Sweetgrass County", or "Mel- 
ville." Fish Creek is a minor stream draining less than half of the 
region especially considered. Bear Butte is a small and marginal 



14 BULLETIISr 16 9, UNITED STATES NATIONAL MUSEUM 

topographic feature. Sweetgrass County does not include some of 
the most important localities, and does include a vast area, much of 
it south of the Yellowstone, far outside that here treated. Melville 
is an unimportant settlement local to one small part of the field. This 
whole region, a great synclinal area with Fort Union rocks filling it, 
may be called the Crazy Mountain region, for these mountains occupy 
its approximate center and are the most prominent topographic 
feature in this part of the State, and the major structure has already 
been called the Crazy Mountain Syncline. The smaller area desig- 
nated and discussed above is, in general, the eastern half of the 
Crazy Mountain region, and is that where the Crazy Mountain Fort 
Union is best and most clearly developed and where it has yielded 
mammals. This area will herein be called the Crazy Mountain Field. 

GEOLOGY 

STRATIGRAPHY 
General Stratigraphic Column 

Rocks exposed in the area between the Musselshell and Yellowstone 
Rivers and east of the Crazy Mountains are from Lower Cretaceous to 
Recent in age. Aside from terrace gravels, moraine and outwash 
deposits, valley fill, and other unconsolidated young deposits, not to be 
considered here, the sedimentary rocks are Cretaceous and Paleocene, 
as far as definitely established. There are numerous igneous intru- 
sions, all younger than the Paleocene sediments, and Kkewise omitted 
from this discussion. The whole stratigraphic column, including 
some rocks not exposed in the area of the map (pi. 1) but all within a 
few miles of these and undoubtedly underlying this area, may be 
summed up in a general way as shown in the column on page 15. 

From exposures outside this area, especially in the Big Snowy and 
Belt uplifts, it appears that the sedimentary rocks here exposed are 
probably underlain by many thousands of feet of earlier Mesozoic, 
Paleozoic, and pre-Cambrian sediments, probably one of the thickest 
piles of sediments in the world. 

The oldest surface beds of this region are exposed only in the centers 
of domes north of the mapped area, for instance in sec. 34, T. 7 N., R. 
16 E. Dr. Barnum Brown has recently obtained some interesting 
dinosaurs from this locality. There is some question whether these 
beds are closer to the Kootenai or to the approximately equivalent 
Cloverley, but here they have generally been called Kootenai. 

The series here called "Undifferentiated Colorado" is probably 
susceptible to definite subdivision and correlation, but this has not 
yet been clearly accomplished and is outside the scope of the present 
study. The lower part was given the local name "American Fork" by 
Douglass (1909), who called the upper, marine, beds "Fort Benton", 



FORT UNIOISr OF CRAZY MOUNTAIN FIELD, MONT. 



15 



Fort 

Union 


No. 3 


Melville 


Dark shales, greenish or 
gray, with numerous gray 
to yellow sandstones. 
Mammals, etc. 


5,000-1- feet. 


No. 2 


Lebo 


Soft somber greenish sandy 
shales and gray sand- 
stones. Mammals, etc. 


850 feet. 


No. 1 


Somber shales with some 
hard brown sandstones. 
Mammals, etc. 


500 feet. 


?Fort 
Union 
(or 
Lance) 


Bear 


Alternating pale cross-bed- 
ded sandstones and shales. 
Rare turtle bones, etc. 
No dinosaurs or mammals. 


500-600 feet. 


Hell Creek 


Pale, variegated clays with 
some gray sandstone. Di- 
nosaurs. 


2,000 feet. 


Lennep 


Brown and yellow sandstone 
and some somber shale. 
Transitional marine-fresh- 
water. 


250-450 feet. 


Bearpaw 


Soft dark shales. Marine. 
(Also some dinosaurs.) 


700-1,100 feet. 


Judith River 


Cross-bedded gray sand- 
stone and sandy shale. 
Dinosaurs. 


400-800 feet. 


Claggett 


Brownish or yellowish thin- 
bedded sandstones and 
shales. Marine to brack- 
ish invertebrates. 


400-800 feet. 


Eagle 


Three prominent coarse 
white sandstones. Coal. 


100-250 feet. 


Colo- 
rado 


(Undifferentiated) 


Upper part soft dark shales, 
locally sandy. Lower 
part with much thin- 
bedded and ripple-marked 
sandstone. Upper part 
marine, lower with dino- 
saurs, turtles, and plants. 


1,300-2,000 feet. 


Kootenai 


Variegated red, green, and 
brown shales and sand- 
stones. Dinosaurs and 
nonmarine mollusks. 


300+ feet (base 
not exposed). 



probably an inexact correlation. Probably equivalents of the Mowry, 
Thermopolis, Frontier, and some other Wyoming formations are 
included. A prominent but local sandstone member has been called 
"Big Elk." 

Douglass at first (1902) called the overlying beds "Niobrara", 
but their more exact correspondence with the Eagle and Claggett is 



16 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

now well established. In 1902 he appUed the name "Fish Creek Beds" 
to the next higher division but later accepted their equivalence to the 
Judith River as established by Stanton and Hatcher (1905). Douglass 
(1909) continued to use the name "Fish Creek" for beds transi- 
tional between Judith River and Bearpaw, but this name is not now 
in general use. 

Lennep is a local name applied by Stone and Calvert to beds perhaps 
equivalent to the Fox Hills but not definitely correlated. In physical 
character they resemble the Lebo, and seem to grade into the Livingston 
laterally. 

Cretaceous — Tektiaey Transition 

It is not proposed to discuss here the general evidence for drawing 
the boundary between the Cretaceous and the Tertiary, a problem to 
which this field contributes only one small part, and not the most 
important part. For present purposes it is assumed that beds up to 
and including the true dinosaur-bearing Lance and Hell Creek and 
their equivalents belong in the Cretaceous and that overlying beds 
without dinosaurs (except by redeposition) and with mammals of 
Tertiary type (including carnivores, condylarths, etc.), from the 
Puerco and its equivalents upward, are to be placed in the Tertiary. 
It is also assumed that the Paleocene is accepted as a separate epoch 
of the Tertiary, of equal rank with the Eocene, Oligocene, Miocene, and 
Pliocene, and that its lower limit is taken as the base of the Puerco 
or equivalent, or the top of the (restricted) Lance or Hell Creek or 
their equivalents, and its upper limit at the top of the Clark Fork, or 
equivalent, or base of the Sand Coulee and Gray Bull, or equivalents. 

On these assumptions, which I believe to be based on the most 
reasonable and useful interpretation of all the evidence, it is here pro- 
posed only to discuss briefly the beds in this field that must include 
the transition from Cretaceous to Tertiary as thus defined and to 
suggest where the boundary may occur in this local series. 

The following is a somewhat generalized section from the Hell Creek 
into the Fort Union No. 1 in sec. 26, T. 6 N., R. 16 E., passing through 
Loc. 65 and near Loc. 78, about 2 miles northeast of the northern 
end of Bear Butte: 

Horizon of Loc. 78 

Feet 

Mostly greenish shales and sandy shales 30 

Somber cross-bedded sandstone, the upper part bard and ridge- 
Fort forming 40 

Union < Somber greenish shale and sandy shale 85 

No. 1 Same, with bone fragments including unidentifiable mammals 

of Tertiary aspect, Loc. 65 7 

Same, without fossils 35 

197 



FORT UNION" OF CRAZY MOUNTAIN FIELD, MONT. 



17 



Bear 



Hell 
Creek 



Zone of hard brown concretions, with numerous fresh-water in- 
vertebrates and some turtle bones ±1 

Transitional beds with shales somewhat darker than those below 

and with local lenses of brown sandstone 15 

Alternating white cross-bedded sandstones and pale shales. .about 485 



about 500 
Softer beds, pale sandstone and clay, with dinosaurs. _ (Not measured) 



Definition of the new name "Bear" is given on page 20. 

All these beds are tilted here, but there is no evidence of angular 
unconformity. The contact beneath the lowest hard sandstone of the 
Bear is sharp but not more so than beneath other sandstones through- 
out this series. Such a contact could, but does not necessarily, 
represent a parallel or erosion al disconformity. The change from 
Hell Creek to Bear is, however, rather more abrupt than from Bear 
to Fort Union No. 1, the latter being transitional through a thickness 
of 15 to 20 feet, the boundary here taken by convention at a local shell 
lens. 

Dinosaurs are found in place, apparently as originally deposited, at 
almost all levels in the Hell Creek, although no very good specimens 
have been foimd in this field. I have seen no dinosaurs in the Bear, 
but Mr. Silberling informs me that he has found isolated, rare, and 
very fragmentary specimens in the lower part of that formation, the 
highest being 80 feet above the base in this section. It is entirely 
possible that these few fragments were redeposited and derived from 
the Hell Creek. No dinosaurs have been found in the upper 420 feet 
of the Bear, but a few champsosaur and turtle bones and some in- 
vertebrates occur. 

Invertebrates from the lens here considered as marking the top of 
the Bear have been identified by Dr. L. S. Russell as follows: 



IFusconaia danae (Meek and Hayden). 
'iNedionidus senectus (White). 
Elli-ptio priscus (Meek and Hayden). 
Viviparus trochiformis (Meek and Hay- 
den). 



Viviparus formosus Meek. 
Campeloma nehrascense whitei Russell. 
Campeloma limnaeiforme (Meek and 

Hayden). 
Physa cf. canadensis Whiteaves. 



Dr. Russell remarks that the three pelecypods range widely in the 
Northwest, Judith River to Fort Union, and that the species of Vivi- 
parus characterize the Fort Union and equivalents (listing mainly 
Upper Paleocene levels), the two Campelomas are likewise from the 
Fort Union or equivalents, and the Physa is of little significance. He 
concludes that the "fauna contains nothing characteristic of the Lance 
and includes several species restricted to the Fort Union. It can be 
regarded with some confidence as Paleocene in age." 



18 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

As already noted, there are no exactly identifiable mammals from 
Loc. 65, but the fragments found here are of Tertiary rather than 
Cretaceous aspect, and the mammals from Loc. 78 are certainly 
Paleocene and probably Middle Paleocene. It seems probable that 
the whole Fort Union No. 1 here is of Middle Paleocene age and all but 
certain that it does not include the earliest Paleocene. 

There are two possible interpretations of this section. First, the 
usual view, in analogous cases, that the Bear is Cretaceous, equivalent 
to part of the Lance, with the necessary corollary here that part of 
the Paleocene, a Puerco equivalent, is probably lacking. This in- 
terpretation is possible, but it seems to me decidedly the less likely of 
the two. The invertebrates indicate Paleocene and probably not 
earliest Paleocene. Even if it be decided that they should be con- 
sidered basal Fort Union rather than uppermost Bear, they are inti- 
mately associated with the latter and in beds that grade into it in- 
sensibly. This gradation itself opposes this interpretation, for it 
makes the presence of an unconformity here, or a gap representing 
Puerco time, seem unlikely. If a break exists it is more likely to be 
within or below the Bear. The absence of dinosaurs, with the pres- 
ence of such reptiles as did survive into the Tertiary, in most of the 
considerable thickness of the Bear is also evidence against this view, 
negative but of some weight. 

The second possible interpretation is that most of or all the Bear 
belongs in the Paleocene, probably representing the Lower Paleocene, 
and that the Cretaceous-Tertiary boundary is in its basal part or below 
it. All the items of evidence mentioned above favor this view. Op- 
posing it are the possible presence of dinosaur bones in the basal Bear 
and the absence of mammals. The dinosaur fragments are, however, 
such as could very readily be redeposited from erosion of the Hell 
Creek, and they are confined to the lower 80 feet of a series about 500 
feet thick. It is entirely possible that there is a disconformity, or at 
least a valid epoch boundary, in this series at the base of a sandstone 
above ther level of these bones, and stUl more likely that the dinosaur 
bones are not really original fossils in these beds. The absence of 
mammals has no weight. Mammals are rare throughout the field as 
a whole, are generally excessively rare in the Lower Paleocene, in this 
field almost never occur in sandstone, which is all that is well exposed 
here, and even if present would be small forms easily overlooked. 
The absence of dinosaurs, however, may well be significant, because 
their bones are large, occur in most terrestrial Cretaceous formations, 
and are very likely to occur where, as here, there are remains of other 
types of reptiles. 

Another summary section through the whole Hell Creek and Bear 
was taken in sec. 15, T. 6 N., R. 15 E. This is continuous with the 
lower Fort Union section of Stanton and Silberhng given elsewhere. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 19 
Base of Fort Union No. 1 



Bear < 



Hell 

Creek 



Feet 

'Clays with thin and inconstant sandstones, a more prominent 

sandstone at the top not well exposed here 280 

Gray to buff platy sandstones in beds usually one to three feet 
thick, with thicker shale partings 330 

610 

Pale variegated shale with occasional soft blocky sandstones. 765 

Pale gray sandstone 10 

Mainly pale variegated sandstone 270 

Heavy gray sandstone, with some shale 145 

Pale white to greenish clays with brown concretionary layers, 

sandstones increasingly prominent toward the top 660 

1,850 
Base of Hell Creek 

Yellow Sandstone and Somber Clay (Not measured) 

Dinosaurs are found in the Hell Creek in this region also, but no 
animal fossils were found in the Bear. 

The discrepancy in thickness of the Bear between this section and 
that previously given, about 110 feet, seems too great to be due 
entirely to difficulty of accurate measurement and is probably at 
least in part a real difference. The localities are about 8 miles apart 
in a straight line. It is also possible that the limits taken do not 
exactly correspond in the two sections, as all the formations concerned 
are highly variable. 

Knowlton (in Stone and Calvert, 1910, p. 749) reports the following 
leaves from "200 feet below the top of the Lance Formation", that is, 
in the Bear at this locality: Sapindus affi,nis, Sapindus grandifoUolus, 
Plat anus aceroides, Platanus sp.?; and the following from a level still 
lower by 200 feet, probably still in the Bear: Sapindus 7 grandifoUolus, 
Sapindus sp., Platanus raynoldsii. Knowlton unreservedly called 
these Fort Union, but this has no bearing on the question here con- 
sidered, since he also called true Hell Creek and Lance floras Fort 
Union. All these species are reported from beds probably of Lance 
age, but they are all equally characteristic, or considerably more 
abundant, in the true Fort Union. 

Throughout the northern part of the field at least, and generally 
except where all the subdivisions of this part of the section tend to 
merge indistinguishably into the Livingston, the beds between the 
Hell Creek and the Fort Union No. 1, or basal Lebo, are a good 
lithologic unit. The scanty data also suggest a distinctive paleon- 
tological character. These facts and the possibility, or as I believe 
probability, that the beds should be classified as Paleocene, or asso- 
ciated with the Fort Union, rather than as Cretaceous and associated 
with the Hell Creek or "Lance" make it highly advisable to distinguish 



20 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

them by a separate name, and I have here called them "Bear",^ from 
Bear Butte around which they are typically developed. They may 
perhaps be equivalent, approximately, to the Tullock, but this would 
be an assumption that might result in serious misapprehension. They 
are far removed from and discontinuous with the type Tullock, into 
which it will never be possible to trace them, and their lithologic 
character is not the same. It is improbable that they are exactly 
equivalent to the Tullock, and even if this should prove to be the 
case it would seem warranted and necessary to retain for them a 
local name. At present correlation with the Tullock would be only 
a guess, which might well prove to be incorrect. 
Typical exposures of the Bear are shown in plate 2. 

Fort Uoton 

The use of the name "Fort Union" has been so loose and ill-defined 
that it has become necessary for every writer who uses it to propose 
his own individual definition or to run the risk of being completely 
misunderstood. In general it has been applied to beds in the Dakotas, 
Montana, and Wyoming, in the northwestern high-plains region (and 
in part intermontane areas) that are, or are supposed to be, later than 
the Lance and earlier than the Wasatch, This apparently satisfac- 
tory definition is in fact most indefinite. In the first place, there 
has not always been general agreement even to this extent, Knowlton, 
for instance, placing beds generally referred to or correlated with the 
Lance in the "Lower Fort Union." In the second place, the definition 
is dependent on that of Lance and of Wasatch, which are themselves 
very ill-defined. It is certain in some areas (notably Polecat Bench 
in northern Wyoming, as shown by Jepsen) and probable in most or 
all that strata generally referred to the Lance, often under the name 
of Tullock but not necessarily equivalent to the type Tullock, are in 
reality distinctly later than the typical Lance or the equivalent Hell 
Creek and both faunally and stratigraphically are more nearly 
related to the overlying beds, that is, to the Fort Union. Thus even 
aside from the question of accurate recognition of the boundaries and 
correlation of members of these formations and groups, there is often 
doubt as to which group should include a given member. The time- 
honored name "Wasatch" is still more ambiguous, to the point that 
very few of the beds called "Wasatch" are really equivalent to any 
part of the type Wasatch. Granted that the use of the name is usually 
intended to imply approximate correlation with the Gray Bull, there 
still remain many doubts as to its proper contents, for there is generally 
a thick series of beds, Tiffany, Clark Fork, and so on, that are some- 

» I am indebted to Miss M. Grace Wilmarth, of the U. S. GeologiealSurvey, for informing me that "Bear" 
and also "Melville" (defined on a later page) are not included in her records as ever having been used 
previously as the names of stratigraphic units. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 21 

times included in "Wasatch", sometimes in Fort Union, and sometimes 
are separated from both as an intervening stage. 

As a matter of personal opinion, I would prefer to use "Fort Union 
group" for the whole Paleocene series of this northwestern plains- 
area, to include all strata of age equivalent to or intermediate between 
the Puerco and the Clark Fork. This usage is very broad, but the 
designation "Fort Union" has already been so loosely applied that a 
more restricted usage would be very difficult to frame or to maintain. 
It at least has the virtue of being on the whole a natural subdivision 
of the Tertiary and of including practically all the beds that have 
ever been called Fort Union, except in out-and-out error or in such 
wholly untenable classifications as that of Knowlton. For more 
precise work it will in any case be necessary to defi.ne and use more 
local names for particular formations and members included in the 
Fort Union group. 

In this field, the earliest workers recognized as Fort Union only 
the beds from the basal No. 3 sandstone (as defined on a later page) 
upward. Douglass, Stone and Calvert, Stanton, and all later workers, 
however, have also included the underlying andesitic beds called Lebo 
by Stone and Calvert. The name "Fort Union" is used tliroughout 
the present study for the Lebo and all higher early Tertiary strata 
in the area here considered. The uppermost part of this series is of 
unknown age and may possibly be as young as the Gray Bull, in which 
case it should be removed from the Fort Union, but at present no 
evidence warrants this step. In addition there is a series of strata^ 
the Bear, hitherto always considered as Cretaceous and referred to 
the Lance, but in my opinion possibly Tertiary. If it should prove 
to be Tertiary, I would place it in the Fort Union, but tliis is now 
doubtful, and in this study the word "Fort Union" is not intended ta 
include the Bear. 

The local Fort Union, thus defined, includes three mappable litho- 
logic units of very unequal tliickness. Mr. Silberling, who first recog- 
nized these units, has applied numbers to them, with Fort Union 
No. 1 at the base and No. 3 at the top, and his field designations have 
been employed in pubUcations by Stanton, Osborn, Gidley, and others. 
In accordance with the general rides of stratigraphic nomenclature, 
local geographic names are here applied, but throughout this discus- 
sion I shall also employ Silberling's numerical designations. The 
correspondence is as follows: 

(No. 3 = Melville (new name) . 
No. 2] 
No. ij ^ °' 

The No. 1 and No. 2 beds are generally similar, and both are 
included in the Lebo of Stone and Calvert, but they are easily sepa- 



22 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

rable throughout the field, and their distinction makes discussion 
and records more exact. Both are said to be in large part andesitic, 
and both are characterized by their somber color, the shales gen- 
erally greenish and the sandstones dark brown, gray, or gray-green. 

The No. 1 beds, or lower Lebo (shown in pi. 2), are characterized 
by numerous lenses and beds of hard and resistant dark sandstone, so 
that this unit is generally topographically positive and forms a ridge 
or series of ridges. This characteristic is visible throughout the 
field; for instance, typically in the gentle anticline in the northern 
part of T. 5 N., Ks. 15-16 E,, where the No. 1 forms an elevated hilly 
area surrounded by a horseshoe valley developed on the No. 2 beds. 
The upper limit of the No. 1 is taken at the top of the highest and 
most persistent of its hard sandstones. The thickness, as measured 
in sees. 15-22, T. 6 N., K. 15 E., is 496 feet (Stanton and Silberling). 
It has not elsewhere been accurately measured. It may be somewhat 
thicker in the western and thinner in the eastern parts of the field 
but apparently does not vary greatly. 

The No. 2 beds are topographically negative (see pi. 3). They 
form valleys between the No. 1 and No. 3 sandstones, or slopes 
beneath the latter. The characteristic material is greenish shale, 
often rather coarse and sandy, with lenses and beds of gray sandstone. 
When unweathered, these sandstones may be hard, for instance in 
the overburden of the Gidley Quarrj^, but they weather rapidly and 
are not resistant to erosion. It is this nonresistant nature of its 
sandstones, and generally their somewhat lighter color, that dis- 
tinguish this member most sharply from the No. 1. The thickness in 
the measured section mentioned above is 840 feet and probably 
averages 800 to 900 feet throughout the field. Stone and Calvert 
(1910, p. 753) give a total thickness of 2,080 feet for the Lebo on Lebo 
Creek. I did not measure the beds here (where they are not very 
well exposed and have a variable and uncertain dip) but estimated 
the thickness at not much over 1,500 feet, with about 600 feet in the 
No. 1 and 900 in the No. 2. They give a total thickness of the Lebo 
in T. 6 N., R. 16 E. (that is, near the north end of Bear Butte) of 
only 463 feet, which I think is surely much too small. It is highly 
unlikely that this persistent formation thins out from 1,334 to 463 
feet in less than 8 miles. The dip in this region changes rapidly, as 
the beds are around the Bear Butte syncline, and exposures are not 
continuous, so that exact measurement is not possible, but it is unlikely 
that the thickness is much if any less than 1,200 feet here, with some 
700 or 800 in the No. 2 and 500 or 400 in the No. 1. 

The Lebo as a whole forms a narrow band along the northern edge 
of the field, from the northeastern end of the Crazy Mountains almost 
due east, but with some sinuosity, to sec. 23, T. 6 N., R. 15 E. Here 
they turn abruptly southward, and their exposure widens greatly 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 23 

under the influence of the Widdecombe Creek antichne, the axis of 
which is mostly on the lower Lebo, with the upper Lebo forming a 
horseshoe valley around it, the eastern limb being occupied b}^ Widde- 
combe Creek. The exposures then swing around the northern end of 
Bear Butte (with the No. 2 also continuous through the gaps across 
the axis of the Bear Butte syncline) and then swing southward and 
widen until they form a very wide area of low relief in the vicinity of 
the Glass Lindsay lakes (Lake Adam and Lake Walvoord). The upper 
limit against the No. 3 swdngs abruptly westward in sec. 34, T. 4 N., 
R. 15 E., and runs over to the Crazy Mountains, which it reaches 
some 17 or 18 miles south of its northern departure from those moun- 
tains. The exposure as a whole thus forms a great loop closed on the 
west by the mountains, as shown in plate 1. 

The No. 1 and No. 2 beds seem to be perfectly conformable and to 
intergrade, forming a natural unit, sandier in its lower part, so that 
the single name Lebo for both is acceptable. In the northern part of 
the field they are generally sharply separable, but in the south it is 
often difficult to distinguish them. It is to be noted, however, that in 
this southern area they are nearly horizontal and are very poorly 
exposed and that in this direction all subdivisions, even between 
undoubted Cretaceous and Tertiary, tend to break down or to be 
very difficult to distinguish. 

The best exposed section shoAving the whole thickness of the Lebo 
is in sees. 15-22,^ R. 6 N., T. 15 E., where it has been measured by 
Stanton and Silberling who give the following section (Stanton, 1909, 
p. 263, here slightly modified): 

No. 3 { Massive sandstone (Not measured) 

Feet 

Shale with a few thin bands of sandstone 112 

Gray sandstone 5 

Shale 18 

Gray limestone, weathering brown [a concretionary layer, not a 
No. 2^ continuous stratum] 3 

Greenish-gray somber shale with much soft sandstone of same 
color and brown .... concretions in lower third, a few thin 
bands of sandstone in upper part and several concretionary 

. zones near top 700 



No. 1 



838 

(Brown, thinly cross-bedded sandstone forming .... ridge 32 

[Somber greenish] shale 200 

Greenish-gray sandstone 15 

Greenish-gray ehale 249 

496 

A section of the underlying beds at this same locality is given on a 
previous page. 

> Stanton says sec. 15, but the greater part of the beds are here in the adjacent sec. 22. 
119212—37 3 



24 BULLETIN 16 9, Lt^ITED STATES NATIONAL MUSEUM 

Stone and Calvert and others have given other sections, but they 
are too generalized or include too many unexposed parts to be very 
helpful. 

The Fort Union No. 3 beds (see pi. 6) are a great mass at least 4,000 
feet thick, and possibly as much as 6,000 if the highest strata of this 
series in the Crazy Mountains be included. Determinable fossils are 
known only from the lower 3,000 feet, and this is the part to wliich 
attention has been particularly directed. In spite of the great thick- 
ness and heterogeneity, there is no convenient lithologic or paleonto-^ 
logical basis for subdividing the beds. They consist of shales and sand- 
stones, most of them lenticular and highly variable. The usual topo- 
graphic expression is a series of ridges on the sandstones and valleys 
on the shales. The shales, particularly at the mammal localities, do 
not differ greatly from those of the No. 1 and No. 2 in appearance, but 
the sandstones are lighter in color and are generally more resistant than 
those of the No. 2. Since the shales are poorlj^ exposed, the general 
impression is of a much paler formation than the underlying Lebo. 
The massive basal No. 3 sandstone is the most continuous and prom- 
inent horizon marker in the Fort Union of this field and has been 
remarked by everyone who has worked here. It almost everywhere 
forms a prominent scarp, and its resistance to erosion is the cause of 
the elevation of Bear Butte, Lion Butte, and numerous less notable 
hills and escarpments. 

The base of this sandstone forms a natural division plane throughout 
the field and is evidently an erosional disconformity, although it is 
unlikely that it marks any considerable time gap. The sandstone 
tends to become less massive in the southern part of the field toward 
the south end of Lion Butte and where it swings westward to the 
mountains, and it is here generally more platy and formed by numerous 
thin beds with shale partings but can be traced continuous^ almost to 
the mountains. 

The fiuviatile nature of these beds and the presence of numerous 
channel and flood sandstones make it possible that there are discon- 
formities at almost any level, but none can be detected as of any regional 
significance, and the whole series seems to be essentially continuous 
and without any noteworthy or sudden change in general type of 
sedimentation. 

The base of the No. 3 is further made noticeable, especially from 
the air, by almost everywhere supporting a growth of evergreens 
(pis. 3, 5). This is the more noteworthy because the sandstones of 
the No. 1 beds, even where almost identical with those of the No. 3 
in topography and elevation, do not support any trees, and the Lebo 
in general is almost devoid of large vegetation except for cottonwoods 
along the stream courses. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 25 

The No. 3 beds occupy an irregular area, somewhat more elongate 
east and west than north and south, bounded by the Crazy Mountains 
on the west and by the loop of Lebo exposures on north, east, and 
south (pi. 1). 

From their position over the Lebo, it may be supposed that the 
No. 3 beds correspond in their lower part to the Tongue River and 
perhaps in their upper part to the Sentinel Butte, but such a correla- 
tion is at present totally unwarranted. They are very distant from 
the typical or from any unquestionable exposures of the Tongue River 
or Sentinel Butte, their litholog}^ is no more like either Tongue River 
or Sentinel Butte than like many other formations and certainly is not 
close enough, in itself, to warrant correlation \\dthout tracing them 
laterally continuously or nearly so into true Tongue River and Sentinel 
Butte, which is impossible. Their age is well established, in part, as 
brought out below under "Correlation", but that of typical Tongue 
River and Sentinel Butte is not, and paleontological correlation wdth 
those members is not now possible. 

Under these conditions it is certain!}^ less helpful than conducive to 
serious error to adopt the frequent practice of assuming that a corre- 
lation exists. Still worse is the practice, also exemplified by some 
work on the Fort Union, of assuming that both Tongue River and 
Sentinel Butte must occur here and dividing the beds, in which no 
natural division has been established in the field, according to the 
proportionate thickness of these members in a widely different area. 

I therefore propose the local name Melville for the lithologic unit, 
from the town of Melville, which is situated on these beds and is 
surrounded, within a few miles, by excellent and typical exposures of 
them. The lower boundary of the formation is well established, as 
shown on the accompanying map. The upper boundary is still 
uncertain. The name is proposed to include at least the lower 3,000 
feet of the No. 3 beds, to about the top of Cay use Butte, and tenta- 
tively for the whole No. 3 of this field, to the highest sediments on 
Porcupine Butte. Later discoveries might make it advisable to 
remove some of these uppermost strata from the formation, and the 
pertinence of still higher beds around the mountain flanks is wholly 
dubious. 

Concretions are common throughout the Fort Union here. Limy 
concretions, weathering rusty yellow, may be of great size, up to 10 
feet or more in greatest diameter, and locally characterize a definite 
stratum, but these appear to be truly concretionary and not a true 
sediment or limestone. Shell limestones do occur locally in the No. 3 
beds, but in the No. 1 and No. 2, while shells may be fairly abundant 
in relatively small lenses, they are generally in a shale matrLx and do 
not form a true limestone. In the No. 3 beds there are a few thin 
bands of comminuted shells, or shell breccia (notably at the Scarritt 
Quarry), generally mixed with clay. 



26 BULLETIX 16 9, UNITED STATES XATIOISrAL MUSEUM 

The relatively small quantity of carbonaceous material is note- 
worthy in ail three subdivisions. There are a few thin impure and 
local lenses of coal in the No. 3, and a little prospecting has been done 
on these, but none are of any commercial value. Aside from these 
thin seams, generally only an inch or two thick, there are a few car- 
bonized tree trunks, occasional very local lenses of coal a few feet in 
diameter and less than an inch in thickness, and locally many minute 
carbon fragments and filaments. In marked contrast with the Fort 
Union of most other areas, these rocks can be classed as not coal- 
bearing. 

Several workers, especially Stone and Calvert and Silberling and 
I, have attempted to follow out the development of this Fort Union 
series into regions beyond the local field, but with indifferent success. 
To the eastward it ends against the Cretaceous, and the Fort Union 
reappears, considerably modified in thickness and character, after a 
long gap, in the Bull Mountain Field (see Woolsey, Richards, and 
Lupton, 1917; also Ellis and Meinzer, 1924). The lower part of the 
Fort Union is there predominantly a shale member, dark and greenish 
in color, with some sandstone (not closely similar to that of the No. 1 
in the Crazy Mountain Field) and coal, about 200 to 300 feet in 
thickness. This is commonly correlated with the Lebo, which is 
probable on lithologic grounds, but there is no evidence that it repre- 
sents the whole Lebo or that it is not a lithologic facies of somewhat 
different span in time. The correlation is here more probable than 
in any other area where the Lebo is supposed to occur, but it cannot 
be considered as established bej^ond doubt. The upper part of the 
Fort Union is here only 1,650 feet thick and contains more pale shale, 
more and different limestone, more numerous and persistent hard 
sandstones above the base, and much more coal than does the No. 3 
of the Crazy Mountain Field. The Bull Mountain Fort Union is an 
isolated mass, completely surrounded by Cretaceous outcrops. 

The Fort Union encircles the Crazy Mountains, which are formed 
principally by intrusive masses thrust into it, and has been followed 
in some detail by Stone and Calvert (1910). (Silberling and I have 
also made a reconnaissance around the mountains on which, as well 
as on Stone and Calvert, my remarks are based.) The Upper Creta- 
ceous formations and the Lebo, steeply folded and much disturbed 
and altered by later igneous activity, swing around and into the 
northeastern end of the mountains. The Hell Creek here appears to 
contain more andesitic debris and comes to resemble more closely the 
Lennep and the Lebo. Toward the southwest, and southward on the 
western flank of the Crazies, the Hell Creek, Bear, and Lebo have not 
been distinguished. It seems probable that they here merge litho- 
logically with the Livingston, as Stone and Calvert believe, or they 
may possibly be absent. There remains, however, the possibility 



FORT UNIOX OF CRAZY MOUNTAIN FIELD, MONT. 27 

that more detailed study and discovery of fossils, especially verte- 
brates, would permit their differentiation here. West of the moun- 
tains the late Cretaceous and early Tertiary strata are thi'own into a 
series of folds, rouglily parallel to the mountain flank and udth north- 
south trend. There is no wide zone of Fort Union, as east of the 
mountains, but strata lithologically similar to the Fort Union do occur 
in narrow zones, as folded. Some of them are almost identical in 
character with the Melville beds of the eastern flank and include 
abundant leaves. This Fort Union facies, overlying the Livingston, 
also occurs in the southern part of the mountain area, but it is much 
disturbed and poorly exposed and not enough work has been done to 
trace its continuity with the well-differentiated series in the north- 
eastern area. It is probable, as Stone and Calvert suppose, that it 
includes only the upper part of the Fort Union of the latter region. 
No mammals have been found in it.'° There is a large area litho- 
logically like the Melville around the southeastern flank of the 
mountains also, but here again exact correlation is impossible at 
present, and considerable search has not yet revealed any mammals 
or other fossils indicative of exact age. 

The Fort Union exposures are siu-rounded by older rocks throughout 
the northern and western areas, and no extension or correlation of 
the beds in these directions is possible. 

Following the beds southward, the division between the No. 1 and 
No. 2 tends to break down, and this is probably true also of that 
between the Hell Creek, Bear, and No. 1 Fort Union near the Yellow- 
stone River. The beds here take on a violet hue, especially the 
shales, a color also seen in the northern area but there rare and here 
predominant. The indivisible beds so colored apparently include the 
Lebo, probably the lower part of the Melville, and also extend down 
into the Cretaceous — that is, this part of the series is blending into 
the undivided Livingston, as reported by Stone and Calvert. 

There is a dark sandstone that may represent part of the No. 1 
Fort Union skirting this area and visible near the 4,700-foot contour 
on the south of the divide between the Yellowstone and Stillwater 
Rivers, south of Reed Point, and also apparently at Absarokee, but 
the identification is uncertain. If this is the No. 1, it represents the 
farthest point to which a definite subdivision of the Crazy Mountain 
Fort Union can really be traced, even in this highly dubious fashion, 
as far as I have been able to ascertain. We were unable to establish 
any continuity with the Red Lodge or Polecat Bench areas, and 
lithologically the beds in those areas are not comparable to those of 
the Crazy Mountain Field, nor are similar subdivisions recognizable. 

'" About 1910 a sheep herder showed Mr. Silberling a jaw of an animal similar to Pantolambda that he said 
was found near the head of Shields River, or between it and Potter Creek. It was impossible to obtain the 
specimen for exact identification or to verify its reported origin. 



28 BULLETIX 16 9, UXITED STATES NATIONAL MUSEUM 

They include nothing really comparable with the Lebo, and the re- 
semblance to the Melville is too vague to have any real correlative 
value. Paleontological correlation alone seems to have any sig- 
nificance between this region and that near the Crazy Mountains. 

STRUCTURE 

The beds of this field are almost nowhere exactly horizontal and in 
places are steeply tilted. Even in the course of purely paleontological 
work it is necessary to take strict account of the structure, since 
relative levels between the numerous isolated exposures can seldom 
be measured directly but have to be calculated from the structural 
data. 

Along the north side of Fish Creek, from the mountains eastward 
to sec. 23, T. 6 N., R. 15 E., there is a strong monoclinal flexure dip- 
ping south at angles of about 40° to 75°. North of this fold only 
Cretaceous beds are exposed. The flexure itself involves the upper- 
most Cretaceous, Bear, Lebo, and basal Melville. The strike is 
sinuous but is mainly east and west to the end of the Crazy ^fountains, 
where the Melville beds mostly run into that range, while the lower 
beds swing around its northern end. In the section noted, this fold 
ceases to affect the Fort Union beds, w^hich are affected south and 
southeast of here by a broad anticline with northeast-southwest trend 
and low dips up to about 12°. Erosion along the axis of this anticline 
has formed a great embayment, about 6 miles wide at its mouth and 
of about the same depth, north and south, surrounded by a high rim 
on the basal Melville. Widdecombe Creek flows along the soft No. 2 
zone on the eastern limb of the anticline. Directly east or southeast 
of this anticline is a parallel syncline the axis of which is occupied by 
remnants of the basal Melville sandstone rising abruptly above the 
No. 2 slopes and valleys. Puet Creek cuts deeply into this, separating 
the axial elevation into the long isolated Bear Butte to the northeast 
and Lion Butte, to the south and connected with the great mass of 
No. 3 beds extending westward to the mountains. 

The Hell Creek, Bear, and Lebo swing around the north end of 
Bear Butte, dipping toward it. The dip increases in intensity here 
away from the actual Butte, until in the upper Hell Creek northeast 
of the Butte it reaches about 30°. The Lebo flanks the long east scarp 
of Lion Butte with low dips, usually 4° or 5°, toward the latter, vari- 
able and afi'ected by slight local disturbances. South of here, toward 
the Glass Lindsay Lakes, the Lebo is nearly horizontal, with dips up 
to 1° or 2°, erratic in direction but oftener to the west. 

Over the greater part of the Melville beds area, south of the strong 
monocline and west of the Widdecombe Creek anticliae, the dips are 
prevailingly westward and fairly consistent at 4° or 5° over a large 



FORT UXION OF CRAZY MOUNTAIN FIELD, MOXT. 29 

area, to the western part of T. 5 N., R. 14 E. Here the wide pass 
between Porcupine Butte and Cayuse Butte is in the very broad, 
poorly marked syncline or basin. The beds around Porcupine Butte 
dip northeasterly into this area, although in the Butte itself the dip 
(about 5°) is nearly north. 

There are a few visible small faults with a throw of a few feet, such 
as one at the Silberlmg Quarry, but these are negligible in beds of 
such great thicloiess. No faults of sufficient importance to show on 
the map or to affect stratigraphic leveling significantly were detected. 

The deformation appears to have been entirely post-Fort Union, 
and nowhere in this region was any angular discordance detected 
between the various Cretaceous and Tertiary formations, even down 
into the Lower Cretaceous (Kootenai) in the domes north of this 
area. It is a reasonable assumption that the deformation was approx- 
imately contemporaneous with the post-Paleocene igneous intrusions. 

FOSSIL LOCALITIES AND FAUNAL LISTS 

GENERAL OCCURRENCE OF FOSSIL MAMMALS 

Fossil mammals, represented at least by material adequate to show 
its mammalian nature, have so far been found at 57 locahties in this 
field, of which about 35 have yielded material sufficiently well pre- 
served for generic identification, and about 25 material specifically 
identifiable and of some real value in correlation and faunal studies. 
The great bulk of the collections comes, however, from the three locali- 
ties where quarries have been developed. 

Although some of the more resistant sandstones, such as those in 
the No. 1 beds or the basal sandstone of the No. 3 beds, are well ex- 
posed and form more or less continuous outcrops wherever they occur 
in the field, the finer and less resistant sandstones and the shales and 
clays are on the whole very poorly exposed. Bones are occasionally 
found in the sandstones, but they are there very rare and are generally 
of no value. Only one identifiable mammal has ever been found in a 
true sandstone in this field. The mammal locahties are therefore 
almost entirely on the rarer shale exposures, which occur where coulees 
have cut the shale slopes or where the wind has developed blow-outs. 
Such exposures, seldom as much as a hundred yards in diameter and 
generally much less, are limited in number. In the productive area in 
this field there are probably not over 400 of them, and all of these have 
been prospected by Mr. Silberhng, manj^ of them also by me or others. 

The mammal occurrences may be grouped under two categories, as 
surface localities or as (actual or potential) quarries. At the surface 
localities, much the more numerous of the two, the mammal remains 
are rare, as far as loiown, and are so sparsely scattered through the 
matrix that only accidental finds or concentration from long weather- 
ing and wind erosion leads to any production. The ideal conditions 



30 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

at such localities are deep weathering in situ without erosion or surface 
drift or wash, combined with gentle deflation, which removes the 
small weathered shale particles but leaves the larger or heavier fossils. 
Such conditions are relatively rare, and it is also noteworthy that 
numerous localities that were in good collecting condition when first 
found 30 years or so ago have now lost much of their value or promise 
by drifting over of windblown material or surface wash, by the spread 
of vegetation onto their weathered surfaces, or by active erosion, 
which removes the surface concentrates and leaves only a clean, hard 
shale exposure in which there is little chance of finding a fossil in situ. 

The quarry localities are those where fossils are so concentrated in a 
local pocket that it is profitable to work the bed as a whole and recover 
fossils in place. The difference is, of course, of degree and not of 
kind but is one of great practical importance. Were it not for its 
three principal quarries, which have been called the Gidley, Silberling, 
and Scarritt Quarries, this field would be of relatively little importance. 
There are marginal locahties also of some importance, intermediate 
between quarries and straight surface localities. Thus Loc. 81 (as 
listed below) was hterally a quarry, but the whole bone pocket and 
therefore quarry was only about a yard in diameter. Loc. 25 has 
yielded so much surface material that a concentration of probable 
quarry calibre is indicated, but the rather limited attempts made 
to quarry at that locality have not in fact developed a profitable 
bone layer. 

An outstanding characteristic of the field, regardless of level or 
geographic position, is the fragmentary nature of the material. In 
the hundreds of specimens collected, there are so far Imown only four 
or five mammal specimens complete enough to be called skulls, and 
only two of these really adequately reveal most of the skull structure. 
Only about 10 specimens include associated upper and lower teeth, 
and only three any surely associated limb bones. Nothing approach- 
ing a complete skeleton has ever been found. This fragmentary con- 
dition is seen not only in the surface specimens but equally in those 
found in situ deep in the quarries. The quarry specimens commonly 
show fresh breaks that look recent and yet abut against undisturbed 
matrix. It is also peculiar that most of the quarry specimens had 
lost some of their teeth before burial and that jaws quite devoid of 
teeth are relatively abundant. 

For his own records and in connection with the National Museum 
collecting, Mr. SilberUng has numbered every locality where any fossils 
were found. These serial numbers are here adopted and are those used 
throughout the present work. There are now 82 numbered localities; 
25 of these are not mammal localities, but for completeness and the 
convenience of later workers they are all given in the serial list on a 
later page. The map (pi. 1), however, shows only mammal localities. 



FORT U]S'ION OF CRAZY MOUNTAIX FIELD, MOXT. 31 

THE GIDLEY AND SILBERLING QUARRIES 

The greater part of the National Museum collection, about four- 
fifths of the identifiable specimens, is from the Gidley and Silberling 
Quarries, of which the Gidley Quarry is far the more important, with 
nearly seven times as many specimens as the Silberling Quarry. 

The Silberling Quarry, Loc. 1, was located, as a surface prospect, 
by Mr. Silberling in 1902, and he subsequently made a small collection 
here that formed the basis of Douglass' publication in 1908. In 1908 
Silberling opened the quarry for the National Museum and then 
collected most of the specimens kno^v^l from this locality. In 1909 
the much richer and more easily worked Gidley Quarry drew his 
attention away from the Silberling Quarry, and httle work has since 
been done there. Silberling has done some farther prospecting, 
however, and in 1935 the Third Scarritt Expedition reopened the 
quarry and worked it for a few days, but abandoned it on finding the 
bed bone poor, the stripping very difficult, the fauna essentially 
duplicating that of the Gidley Quarry, and the matrix unsatisfactory 
from the point of view of preparation. This quarry did, however, 
produce the splendid Ptilodus skull and partial skeleton described 
by Gidley, and it is the only locality in this field where Psittacotherium 
or Elpidophorus minor have been found. All its other genera and 
species are represented by about equally good or better material 
from other localities. 

The Silberling Quarry is in NE'^SWK sec. 4, T. 5 N., R. 16 E., 
in an embayment near the middle of the east side of Bear Butte 
(see pi. 5). The fossil horizon is about 75 feet below the base of the 
No. 3 sandstone and is the highest level in the No. 2 that has yielded 
identifiable mammals. The bone layer is not well defined by any 
visible criteria but is limited to a zone 1 or 1}^ feet in thickness. 
The matrix is a fine greenish tuft" or shale, very tough and harsh, 
extremely abrasive to handle, and difficult to work in preparation. 
It grades laterally into a bed with numerous fresh-water bivalves, 
among which mammals also occur, but this matrix is so hard that 
preparation of fragile specimens would be almost impossible. 

The Gidley Quarry, Loc. 4, is in NW}4'NE}^ sec. 25, T. 5 N., 
R. 15 E. (see pi. 4). It is immediately adjacent to the county road, 
on its east side, where it descends the steep hill from the basal No. 3 
rimrock to the valley of the upper part of Widdecombe Creek, on 
the relativel.y unresistant and topographically negative No. 2 beds. 
A small coulee here descends the slope, in a westerly direction, and 
cuts the bone bed apparently near the middle of the rich pocket in 
which the Gidley Quarry is developed. The locality was discovered 
by Mr. Silberling as a surface prospect in tliis coulee in 1905. When 
Dr. Gidley visited the field in 1909, Mr. Silberling showed liim this 
locality as the most promising of any in the field. The surface 



32 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

material was unusually abundant but so disintegrated as to have 
little value. Dr. Gidley dug in along the bone stratum until firmer 
material was found in place, made a good collection from this bed, 
and thus started the quarrying operations that Silberling and others 
have continued intermittently ever since. Mr. Silberling's opera- 
tions for the National Museum, resulting in the bulk of the collection 
here described, consisted in stripping and working out an area of 
about 1,400 square feet (a very rough estimate). The other important 
operation, that of the Third Scarritt Expedition in 1935, extended 
over an area of about 1,750 square feet (also a rough approximation, 
as the area was irregular and not all uncovered at once). 

The quarry consists of two cuts, one north and one, of smaller size, 
south of the coulee and original surface exposure. The material 
collected by Silberling was carefully labeled as to the cut from which 
it came, but in this study there was found to be no significant differ- 
ence between the two parts of the collection, and it is all treated as 
a unit. The greater part of the worked-out area has been filled in 
again in later stripping, and the cuts left open weather and fill rapidly, 
so that the form of the quarry is not apparent in the field. The north 
section has probably been about worked out, except for a probably 
very rich corner left under heavy overburden. The south section 
was still rich along the margin as left in 1935 and probably would 
produce over an area of at least 1,000 square feet, and possibly 1,500, 
before the bone layer ran out into the hillside, so that the locality 
as left in 1935 is, as far as such things are predictable, still capable of 
producing another collection about as large as either of the two so 
far made there. The quarry has so far produced about 800 good 
identifiable mammal specimens and perhaps 1,500 single teeth and 
other unimportant fragments. 

The areal distribution of the fossils is very erratic and patchy. 
In places it is possible to work for 1 or 2 days without finding any 
jaws, and in others one man can collect ten or more jaws in a day. 
In general, however, the fossils seem to be distributed in an elongated 
area, about 5 to 20 feet in width, usually nearer the smaller figure, 
and with a tested length of at least 150 feet, which probably will 
continue to a much greater distance. The general trend is north- 
northeast to south-southwest. 

In many places the fossils are concentrated in a single and fairly 
well defined layer an inch thick or even less in which fragments of 
bone may be so numerous as nearly to make a bone-bed. This 
material is, however, very fragmentary, and good jaws are exceptional 
in it. In other places the bone layer is less definite, and the fossils 
are scattered more sparsely but generally in better preservation through 
a thickness of about a foot, or up to about 18 inches at most. Oc- 
casional fragments are found in the nearly barren material above and 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT 



33 



below this more definite fossil horizon but (as far as observed) onl^ 
within a few inches of it. The level is about 125 or 150 feet below 
the base of the No. 3 sandstone. Some additional remarks on the 
occurrence of fossils here are made in discussing the facies and ecology 
of the quarry fauna. 

Table 1 gives a complete list of the fossils so far identified from the 
Gidley and Silberling Quarries, with the number of upper and of 
lower jaws of each species, based on the National Museum collection 
only except Elpidojphorus minor, the one specimen of wliich is in the 
Princeton Collection. It is probably, but not quite sureh^, from the 
Silberling Quarry. 



Table 1. — Fossil mammals so far identified from the Gidley and Silberling Quarries, 
Crazy Mountain Field, Mont. 



Species 



Gidley Quarry 



Upper 
jaws 



Lower 
jaws 



Silberling Quarry 



Upper 
jaws 



Lower 
jaws 



Multitubeeculata: 
Ptilodontidae: 

Ptilodiis montanus 

fPtilodus douglassi 

tPtilodus gidteyi 

fPtilodus sindairi 

Ptilodus sp 

fEciypodus grangeri 

tEciypodus russetti 

fEciypodus silberlingi 

fPareclypodus jepseni. 

Eucosmodon sparsus 

Insectivora: 

7Deltatlieridiidae: 

Oetastops parous 

Leptictidae: 

Prodiacodon concordiarcensis. 

Leptacodon ladae. 

Leptacodon munasculum 

Myrmecoboides montanensis.. 
Nyctitheriidae: 

StUpnodon stmplicidens 

Pantolestidae: 

Bessoecetor dilucuti 

Aphronorus fraudator 

Mixodectidae: 

Eudaemonema cuspidata 

ElpidophoTus minor 

Picrodontidae: 

Picrodus silberlingi 

Primates: 

Plesiadapidae: 

Pronothodectes mattheici 

Carpolestidae: 

Elphidotarsius florencae 

?Anaptomorphidae: 

Paromomys maturus 

Paromomys depressidens 

Palaechthon alticiispis 

Patenochtha minor 



39 



34 



BULLETIN 169, UXITED STATES NATIONAL MUSEUM 



Table L — Fossil jnammals so far identified from the Gidley and Silberling Quarries, 
Crazy Mountain Field, Mont. — Continued 





Gidley Quarry 


Silberling Quarry 


Species 


Upper 

jaws 


Lower 
jaws 


Upper 
jaws 


Lower 
jaws 


Taeniodonta: 

Stylinodontidae: 

Conorydes comma 


1 




1 

1 




Psittacotherium muUifragum 






Cabnivoea: 

Arctocyonidae: 

Claenodon montanensis 


1 

1 


2 

1 
1 
2 
11 
1 
4 




Claenodon silberlingi 




Claenodon latidens 




Claenodon sp. 






Prothryptacodon furens 




1 


Metachriacus punitor 


3 




3 


Spanoxyodon latrunculus 






Mimotricentes latidens... 




2 


MimoMcentes angustidens 






1 


Miacidae: 

Bidymictis microlestes 


4 


13 
1 


1 
1 


1 


Didy mid is tenuis. 




Didymidis fhaydenianus 






Ididopappus mvLstelinus 


1 


1 
1 

34 
9 
3 

7 




Mesonychidae: 

Dissacus sp 


1 


Condylarthha: 
Hyopsodontidae: 

Ellipsodon aquilonius 


17 
2 
2 
2 


1 


7 


Litaletes disjundus 




Litomylus dissenianeus . . 




Haplaletes disceptatrix 




Phenacodontidae: 

Tetradaenodon symboticus 


1 


Tetradaenodon cf. puercensis... 


2 

1 
4 


6 
3 

2 
1 






Periptychidae: 

Coriphagus montanus 


1 


Anisonchus sedorius. 






Pantolambdidae: 

Panlolambda intermedias 




Pantolambda sp 












Totals 


[ 107 


275 13 45 
382 58 






440 





THE SCARRITT QUARRY 

The fauna of the Scarritt Quarry is not described in this memoir, 
being known only from material in the American Museum that has 
been published separately, but it is included in the faunal lists here 
given, and a general discussion is essential in the present consideration 
of the field as a whole. This locality, Loc. 56, was found by Mr. 
Silberling years ago and a few surface fragments collected. He located 
the bone layer and planned to attempt quarrying, but this plan was 



FORT UNIOX OF CRAZY MOUNTAIN FIELD, MONT. 35 

not carried out until 1935, when the Third Scarritt Expedition opened 
a quarry here and made a collection of about 50 jaws and numerous 
teeth and odd fragments. The locahty is in SE)^NWK sec. 13, T. 5 N., 
R. 14 E., on the eastern slope of the low divide or spur that extends 
northward from Cayuse Butte. The horizon is estimated to be about 
2,000 feet above the base of the No. 3 beds, hence about 2,150 feet 
above the Gidley Quarry and about 3,350 feet above the base of the 
recognized Fort Union of this area. As it is quite impossible to 
measure a continuous section between any of these datum planes, the 
horizon is approximate only but is probably of the right order, and 
the quarry is unquestionably much higher stratigraphically than the 
other quarries, and the highest in the field from which much identi- 
fiable material has been found except for Locs. 11 and 13, which are 
clearly higher, probably by about 1,000 feet. 

The fossil level is marked by a bed, varying from a mere film up to 
about 4 inches in thickness, almost entirely composed of shell frag- 
ments. Mammals occur in this shell bed, and also in the clay (with 
more scattered and more complete shells) within 2 or 3 inches of it, 
both above and below. As far as the bone pocket has been followed, 
it is much less rich than the Gidley Quarry, but the material is good 
in average preservation and association of upper and lower jaws is 
relatively much more frequent than in the other quarries. (Four 
instances of association occur among the 50 jaws collected here, while 
such association has so far been found only once in the Silberling 
Quarry and once in the Gidley Quarry.) The fauna so far collected 
is as follows: 

Ectypodus hunteri: 2 upper and 4 lower jaws and 27 isolated teeth. 

Ptilodontid undetermined: 1 tooth. 

Leptacodon cf. tener: 1 lower jaw. 

Bessoecetor thomsoni: 3 upper jaws, 9 lower jaws, and 1 specimen with associated 

upper and lower jaws. 
Cf. Palaeosinopa sp.: 1 tooth. 
Elpidophorus patratus: Associated upper and lower jaws, 1 upper jaw, 1 lower 

jaw, and 5 isolated teeth. 
Unuchinia asaphes: 1 lower jaw. 

Plesiadapis anceps: Associated upper and lower jaws and 6 isolated teeth. 
Carpodaptes hazelae: 1 upper and 3 lower jaws. 
Phenacoleniur frugivorus: 1 lower jaw. 
Cf. Chriacus sp.: 1 tooth. 

Litolesles nolissimus: Associated upper and lower jaws and 19 isolated lower jaws. 
Tetraclaenodon sp.: 1 upper molar. 
Pantolambdid undetermined: 2 broken teeth and parts of limb bones. 

OTHER IMPORTANT LOCALITIES 

The following are faunal lists for and some notes on localities other 
than the three quarries that are of some importance. They include 



36 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

all the localities for which mammaHan material that can be identified 
is available, and also one locality of which this is not true but which 
is important as being the highest stratigraphicallv where mammal 
fragments have been found. All these localities merit repeated pros- 
pecting in the future, and any of them may turn up material of out- 
standing importance. The same is also true, but with less probabihty, 
of mammal localities, not especially discussed here but all given in the 
serial locahty list, from which no identifiable specimens are now at 
hand. 

Fort Union No. 1, or Lower Lebo 

Loc. 65.— Sec. 26, T. 6 N., R. 16 E. This is the lowest horizon at 
which mammals have been found in this field, being only about 35 
feet above the base of the Fort Union No. 1, or of the Lebo. It is a 
small shale slope immediately north of the south line of the section 
and on the west side of a wagon trail that follows the base of the Fort 
Union No. 1, on the underlying sandstone ledge. The only identi- 
fiable mammal yet found here is a P4 inseparable from Ptilodus 
sinclairi, mentioned in connection with the systematic description of 
that species. We have recently found here a few scraps of mammal 
bones, also crocodile or champsosaur teeth and ganoid scales, but the 
material is very scanty and poor. This is, nevertheless, the most 
promising prospect for obtaining material near the basal contact of 
the recognized Fort Union in this field. 

Loc. 75.— Sec. 26, T. 6 N., R. 16 E. This locahty is in the same 
section as Loc. 65 but farther west, on the other side of a sandstone- 
capped hill and at a higher level, about 200 feet above the base of the 
Fort Union No. 1. The only identifiable specimen yet found at it 
is the lower jaw made type of Chriacus pugnax. 

Loc. 9. — Sec. 35, T. 6 N., R. 15 E. This is the most promismg 
locality for mammals in the No. 1 beds. It is a good shale exposure on 
the west flank of the Widdecombe Creek anticline, about 200 feet below 
the base of the No. 2 and hence probably about 300 feet above the base 
of the No. 1, although this cannot be measured accurately. Search in 
1935 revealed no new material. Previously the following had been 
collected: Lower jaw fragment of fMimotricentes sp., type upper jaw 
of Claenodon vecordensis, and two upper molars (Princeton no. 13757) 
of Tetraclaenodon fsymholicus. 

Loc. 73.— Sec. 34, T. 6 N., R. 16 E. This locahty is in the somber 
capping sandstone of the No. 1 beds, nearly 500 feet above their base. 
It has yielded only one mammal, a lower jaw of Mimotricentes angusti- 
dens in the Princeton collection. This is the only identifiable mammal 
to be found in a sandstone in tliis field. Subsequent search has not 
brought to light any other fragments at this locality. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 37 

Fort Union No. 2, or Upper Lebo 

The great bulk of the collection is from these beds. The Silberling 
and Gidley Quarries are described and their fauna hsted in a separate 
section of this work. The other No. 2 localities with identifiable 
mammals are as follows: 

Loc. 51.— Sec. 24, T. 4 N., R. 15 E. This is one of the richest of 
surface localities but has yielded no fossils in place. It is in the valley 
of Wildcat Creek, west of the stream, about 75 feet above the base of 
the No. 2 beds. The identifiable mammals are: 

Pucosmodon sparsus: Lower incisor. 

Ptilodus fmonlanus: Broken premolar. 

Mimotricentes angustidens: 2 isolated lower molars. 

Metachriacus provocator: Associated upper and lower teeth, 2 isolated lower and 2 

isolated upper jaw fragments. 
Metachriacus sp: Upper tooth. 

Pidymiciis cf. haydenianus: Broken lower premolar. 
Ellipsodon aquilonius: Lower jaw. 
Litaletes dlsjunctus: Fragment of lower jaw and atypical but probably referable 

upper jaw. 
Tetraclaenodon cf. symbolicus: Upper tooth, 
Anisonchus sectorius: 4 lower jaws. 

Loc. 8. — Sec. 23, T. 6 N., R. 15 E. The exact horizon is uncertain, 
but the locality is near Loc. 81 and probably at about the same or a 
somewhat lower level. The only identifiable fossil is a partial upper 
jaw of Didymictis liaydenianus. 

Loc. 24.— Sec. 2, T. 3 N., R. 15 E. This is near Loc. 25, about halt 
a mile farther southwest, near the shore of Lake Adam, and at about 
the same level, about 300 feet above the base of the No. 2 beds. The 
identifiable mammals are: Associated upper and lower teeth of Meta- 
chriacus provocator, upper tooth of Didymictis microlestes, one upper 
and one lower jaw of Anisonchus sectorius. 

Loc. S5.—Sec. 35, T. 4 N., R. 15 E. Near the north end of Lake 
Adam and about 300 feet above the base of the No. 2 beds. This is a 
rich locality that yields surface material on every visit, but only one 
specimen has been found in place and attempts to develop a quarry 
have so far been unsuccessful. The following have been found: 

JEucosmodon sparsus: Lower incisor. 

T, , , , f All known material. 

Peuterogonodon montanus] c< . .■ ■, • .• 

. „ , , \ See systematic descriptions. 

f JJeuterogonoaon sp. K^. ' 

I Five specimens. 

Metachriacus provocator: 4 lower and 2 upper jaws (in American Museum). 

Tetraclaenodon symbolicus: 9 lower and 1 upper (the upper and 4 lower in the 

American Museum). 

Anisonchus sectorius: 3 lower and 1 upper (the upper in the American Museum). 

Loc. 60.— Sec. 9, T. 3 N., R. 15 E. Tliis is the southernmost local- 
ity in the field, southwest of Lake Adam. The horizon cannot be 
closely determined but is near that of Loc. 25. There is a large but 



38 BULLETIN?" 169, UNITED STATES NATIO^^AL MUSEUM 

almost barren exposure at a small pointed hill and east of this a flat 
and poor but richer exposure where the following mammals were 
found: 

tPtilodus gidleyi: 1 lower premolar. 

Ptilodus montanus: 2 lower premolars. 

Metachriacus provocator: Associated upper and lower jaw fragments and I 

isolated lower. 
Anisonchus sectorius: 1 lower jaw. 

Loc. 81. — Sec. 23, T. 6 N., R. 15 E. This is in the extreme northern 
part of the field where the steep monocline swings into the Widde^ 
combe Creek Anticline, It is in the lower half of the No. 2 beds, 
probably about 300 feet above their base. Mr. Silberling found this 
excellent shale exposure years ago, but nothing was found in it until 
1935, when a small rich pocket of fossil mammals, most of them still 
in place, was discovered. Extensive prospecting failed to uncover 
anything else, and despite its richness this seems to have been a very 
local pocket, only 2 or 3 feet in diameter. The material is in the 
American Museum collection and includes the following forms: 

Aphronorus fraudator: Upper premolar. 

Prothryptacodon ffurens: 1 lower jaw. 

Metachriacus provocator: 1 upper and 3 lower jaws. 

Mimotricentes flatidens: 1 upper and 1 lower jaw, possibly associated. 

Didymictis cf. haydenianus: 1 upper jaw. 

Loc. 5^.— Sec. 23, T. 5 N., R. 15 E. This locaHty is at a large shale 
exposure immediately north of the Gidley Quarry. Fossils have been 
found here at two levels, one about the same as that of the Gidley 
Quarry and designated as Loc. 54, and the other, Loc. 52, about 50 
feet lower. Numerous scraps have been found here, but the only cer^ 
tainly identifiable specimen is apparently associated right and left 
M2 and other fragments of Claenodon montanensis. 

Loc. 4' — The Gidley Quarry occurs at this level relative to th,e other 

localities. It is discussed elsewhere. 

Loc. 5.— Sec. 33, T. 6 N., R. 16 E.l ^, ,, ^ ,. 

r n o o/m/>AT-n-.^T^r Thcse are the two discovery 

Loc. 6. — Sec. 34, T. 6 N., R. 16 E.j "^ 

localities, where Douglass found the first Fort Union mammals in 1901. 

They are at nearly the same level, about 1,200 feet above the base of 

the Fort Union (No. 1), and 125 to 150 feet below the basal No. 3: 

sandstone, about the same level as the Gidley Quarry. Loc. 5 is a 

relatively large shale exposure on the west side of Bear Butte near its 

northern end, readily recognized as being opposite (across the county 

road from) a small, tepee-shaped outlier of the main butte. Loc. 6 is a 

smaller shale exposure about quarter of a mile northeast of Loc. 5 and 

just east, or slightly southeast, of the extreme northern end of Bear 

Butte (see plate 3). Douglass' material from the two localities (with 

identifications slightly amended in the light of later knowledge) was as 

follows: 



FORT UNION OF CKAZY MOUNTAIN FIELD, MONT. 39- 

Tetraclaenodon cf. puercensis: 3 isolated upper teeth. 
Ellipsodon aquilonius: Jaw fragment with M2. 
Anisonchus sectorius: Jaw fragment with P4 and M]. 

Pantolambda spp.: Canine, premolar, and limb bones, perhaps of more than one 
species. 

Subsequent discoveries at Loc. 5 include an unidentifiable multi- 
tuberculate and other fragments, and at Loc. 6 the followdng: 

Conorydes cf. comma: 2 upper molars. 

Tetraclaenodon cf. puercensis: Upper jaw with dm*-M'. 

Pantolambda sp.: Worn and broken upper molar and limb fragments. 

Loc. 54.— Sec. 23, T. 5 N., R. 15 E. This is immediately north of 
the Gidley Quarry and at about the same level, on the same exposure 
as Loc. 52 but about 50 feet higher. The most nearly identifiable 
specimens found here are an isolated lower tooth and limb bones of 
Pantolambda sp. The rich pocket in which the Gidley Quarry is 
developed apparently does not extend this far north. 

Loc. 1. — The Silberling Quarry is the highest mammal locality 
definitel}" in the No. 2 beds and occurs at this position relative to the 
other localities. It is discussed elsewhere. 

Loc. 3.— On line between sees. 11 and 14, T. 5 N., R. 15 E. The 
horizon of this locality has not been determined, but it is in the upper 
part of the No. 2 beds. It has yielded only one lower jaw of Tetra- 
claenodon symholicus. 

Fort Union No. 3, or Melville 

This great upper division has numerous scattered localities, but 
only one (the Scarritt Quarry) has yielded a fauna that can be con- 
sidered of much value. The first two localities here listed, 15 and 70, 
are definitel}^ in the No. 3 beds, probably in their lower part, but of 
unknovrn relative level. The others are here arranged in the order 
of their stratigraphic levels. 

Loc. 15. — Sec. 9, T. 5N., R. 14E. The only identifiable specimen 
from here is a lower jaw fragment indistinguishable from Paromomys 
maturus. The level is uncertain but is above the basal sandstone of 
the No. 3 beds. 

Loc. 70.— Sec. 31, T. 6 N., R. 15 E. The only specimen from this 
locality, also in the No. 3 but of doubtful level, is a lower tooth prob- 
ably of Tetraclaenodon, but possibly Gidleyina. 

Loc. 82.— Sec. 11, T. 4 N., R. 15 E. There is some doubt about 
this locality, as the local section is not clear, but it is probably near 
the base of the No. 3 beds. The only identifiable specimen is asso- 
ciated M^ and broken M^ (in the American Museum) referable to 
Tetraclaenodon cf. puercensis. 

Loc. 53.— Sec. 14, T. 4 N., R. 15 E. This locality is immediately 
adjacent to Loc. 82 and at the same level. It has yielded one upper 
tooth of Claenodon cf . ferox. 

119212—37 i 



-40 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

Loc. 39.— Sec. 15, T. 4 N., R. 15 E. This locality is also near the 
base of the No. 3 beds, and at about the same level as Logs. 82 and 53, 
possibly a little higher. Plere were found a lower jaw fragment of 
Claenodon of. jerox and limb bones probably of a pantolambdid. 

Loc. 12.— Sec. 30, T. 6 N., R. 15 E. This locahty is adjacent to 
the next, Loc. 27, and at a slightly lower level. It yielded an upper 
jaw of Anisonchus sedorius. 

Loc. 27.— Sec. 30, T. 6 N., R. 15 E. This and Loc. 28 are at about 
the same level, 300 to 400 feet above the base of the No. 3 beds, on 
x)pposite sides of the Harlowton-Melville road where it turns after 
descending the "Fish Creek Hill." ^^ The type material of Gidleyina 
.silberlingi is from here. 

Loc. 28.— Sec. 29, T. 6 N., R. 15 E. A httle less than quarter of a 
.mile northeast of Loc. 27 and at about the same level. It yielded an 
upper tooth of a pantolambdid and one identified as cf. Conoryctes sp, 

Princeton Localities 

Under this general heading I group numerous localities in the 
western part of T. 5 N., R. 15 E., and two in the northeastern part 
iof T. 5 N., R. 14 E. The exact localities are given in the serial list 
,and on the map. These localities were found and worked by the Prince- 
ton parties under Farr in 1902 and 1903 and were thoroughly pros- 
pected at that time, the surfaces apparently very well cleared. Air. 
Silberling, Mr. Silberling and I, and the Third Scarritt Expedition 
liave at intervals between 1903 and 1935 gone over these localities 
again, but they have not yielded much new material. In the past 
few years their surface conditions have been increasingly unfavorable 
.for collecting. Mr. Silberling's system of locality records was not 
initiated until several years after the Princeton work, and the locality 
records of the 1902 and 1903 collections, at least as they are now pre- 
served, are very vague and not entirely reliable, especially as these 
parties also collected much material in those years at widely different 
ievels in other parts of the field. There are a number of identifiable 
mammal specimens in the Princeton collections that can be definitely 
placed, on the basis of such records as are preserved and of Mr. 
Silberling's certain recollection of particular specimens, in a cluster 
-of localities all at about the same level. Two more are possibly from 
this general area and level, but not definitely placed. The others 
(eight cataloged specimens) are surely or probably from quite different 
jlevels and locaHties and are mentioned elsewhere. 

Lacs. 36, 38, 40, 41, 42, 43, 45, 57, 59, 60, and 68.—K\\ in sees. 17, 

19, 20, and 29, T. 5 N., R. 15 E., all Princeton mammal locaHties, all 

at approximately the same level, stratigraphic differences probably not 

<over 100 feet (which is generally insignificant in this field) and are 

" As the road was until 1935, at least. Its course may be changed by work then in progress. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 41 

about 900 to 1,000 feet above the base of the Fort Union No. 3 or 
about 2,250 to 2,350 feet above the base of the Fort Union No, 1. 
The following Princeton material seems definitely to be from tliis 
group of locahties. 

Gidleijina monlanensis: Type, as described below; this is from Loc. 68. 

A lot including IGidUyina sp., lower premolar, a lower molar of an indeterminate 

oxyclaenine, and 3 probably associated lower teeth of Anisonchus sectorius, 

all probably from Loc. 42. 
A badly broken lower jaw with 3 imperfect teeth, suggestive of P. cavirictus but 

not that species, perhaps not that genus, prolDably from Loc. 43. 
Gidleyina Imontanensis: A miscellaneous lot including an M^ probably of this 

species; an isolated P4. These are probably from Loc. 60. 
The only approximately identifiable specimen now in the National Museum and 

labeled as from these localities, a lower jaw fragment from Loc. 57, probably 

Gidleyina sp. but possibly Tetradaenodon. 

Loc. 44 is at a sHghtly higher level than those just discussed, prob- 
ably about 200 to 300 feet. It has yielded a large lot of probably 
associated material of Claenodon fjerox and also an upper premolar 
probably pantolambdid but not Pantolambda. Both lots are in the 
Princeton collection. 

Locs. 20, 61, 62, 63, 69 and 72 are also Princeton localities and have 
yielded mammals, but I have been unable definitely to tie in any 
identifiable specimens in the collections to these localities. 

Loc. 56.— Sec. 13, T. 5 N., R. 14 E. This is the Scarritt Quarry, 
which occupies about this position relative to the other localities here 
listed. Its fauna is discussed elsewhere. 

Loc. 18.— Sec. 14, T. 5 N., R. 14 E. This locaHty is nearly a mile 
west-southwest of the Scarritt Quarry, over a gentle hill (running 
north from Cayuse Butte), and at nearly the same level or perhaps a 
little higher. Gidley recorded it as "about 2,000 feet below the top 
of No. 3", and my estimates woidd place it at just about that distance 
stratigraphically below the highest exposures on Porcupine Butte. 
It has yielded a pantolambdid upper tooth, a lower jaw of Anisonchus 
sectorius, and a lower jaw fragment of Ellipsodon sp. 

ioc. .r^.— Sec. 23, T. 5 N., R. 14 E.l ,,,, , ,, , ,.,. 

Loc. IS.-Sec. 22, T. 5 N., R. 14 E.f ^^though these locahties are 

about half a mile apart at their ends and are in different sections, they 
are merely two parts of a series of shale exposures and blow-outs. 
Material from the two marked localities has not been consistently 
separated, nor is there any great need for doing so since they are at 
about the same level and in a more or less continuous series of expo- 
sures. They are high up on Cayuse Butte, or Cayuse Hills, on the 
divide between the Sweetgrass and Fish Creek drainages. Mr. 
Silberling has found numerous fragments on the surface here, and in 
past years the exposure has been good, but in 1932 and still more in 
1935 we found it in poor condition, covered with wash and in places 



42 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

tending to sod over. Efforts have been made to find a bone level or 
develop a quarry, but so far no material has been found in place. 
This series of exposures is important as the highest in this field from 
which identifiable material has been recovered. The level is about 
3,000 feet above the base of the No. 3 beds. The National Museum 
specimens available are: 

Plesiadapis rex: Type and referred material, as described below. 

Cf. Paromomys, genus and species undetermined: An isolated upper tooth. 

IGidleyina superior: Type lower jaw. 

Teiradaenodon sp.: 2 upper molars. 

To this Ust may be added the follomng forms in the Princeton 
collection. Their derivation from this level seems to be estabHshed 
with sufficient probability: 

Multituberculate undetermined: 2 broken premolars. 
Elpidophorus Ipatratus: Lower molar. 
ClaenodoH cf. ferox: 2 upper teeth. 
Thryptacodon cf. australis: Lower molar. 
Hyopsodontid aff. Haplaletes: M^-^. 

Loc. 49.—'NW%'NWy4 sec. 23, T. 5 N., R. 14 E. This is near 
Logs. 11 and 13 in position and also stratigraphically. According to 
Mr. SilberHng, Princeton no. 13756, numerous tooth and jaw frag- 
ments of Claenodon fferox, came from here. 

Loc. 66.— Sec. 14, T. 5 N., R. 13 E. This is a very high exposure, 
at least 750 feet stratigraphically above Loc. 13, on the east flank of 
Porcupine Butte, about one-third of the way up that butte. It is a 
small shale exposure, important only as the highest level in this 
field where mammal fragments have been found. It is also con- 
siderably the most western mammal locality in the field. The 
material collected was, Mr. Silberling informs me, definitely mamma- 
Han, but probably was not identifiable and no specimens bearing this 
locaUt}^ datum were found in the collection. 

Horizon Uncertain 

Here may be mentioned two Princeton specimens that are of too 
uncertain provenience for present inclusion in the more precise Hsts 
or for use in correlation. 

No. 14191 includes two upper molars of a small Claenodon, com- 
parable to C. silberlingi, collected July 3, 1903, labeled as from the 
Torrejon, "Anderson's Big Timber Road", a designation too vague 
to indicate any particular horizon or locality. 

No. 13757, December 1902, "Loc. No. 9 Puerco", is probably from 
the Fort Union No. 1, since the No. 2 was known to be of Torrejon 
age by the Princeton parties and the No. 1 considered as Puerco. 
Loc. 9 of Silberhng's series is in the No. 1, but since the Princeton 
parties did not use these numbers this is probably only a coincidence 



FORT UIs^ION OF CRAZY MOUXTAIX FIELD, MONT. 



43 



and the locality is uncertain. The specimen includes M^~^ appar- 
ently of Tetraclaenodon and comparable to T. symbolicus, but not 
close enough to assure specific identification. 



Table 2. — Serial list of localities, Crazy Mountain Field, Mont. 



No. 


Quarter 


Section 


Town- 
ship 
North 


Range 

East 


Feet above 
base of Fort 
Union No. 1 


Remarks 


1 


NE of SW 


4 

7 
11-14 

23 
33 
34 

25 

23 
35 

15-16 

30 
22 

11-14 

9 
34 

15 
14 
15 

13 

16 

34 
8 
2 
35 
31 
30 
29 
29 
30 

26 

25 
17 
36 
33 
20 
33 
17 
15 
29 
29 
20 
20 


5 
4 
5 

5 
6 
6 
6 

6 

6 
5 

5 
6 
5 

5 

5 
6 

5 
5 
5 

5 

5 

8 
5 
3 
4 
6 
6 
6 
6 
6 

6 

5 
5 
7 
6 
5 
6 
5 
4 
5 
5 
5 
5 


16 
16 
15 

15 
16 
16 
16 

15 
15 
14 

14 
15 
14 
15 

14 
16 

15 
14 
14 

14 

15 

16 
16 
15 
15 
16 
15 
15 
15 
15 

15 

15 
15 
16 
16 
15 
16 
15 
15 
15 
15 
15 
15 


1,265 

(In No. 2)... 
(In No. 2)... 

1,200 

1,200 

1,200 


SlLBERLING QUARET. 


2 

3 

4 . 


NE half of NE quarter- 
On line, near corner 

with 10 and 15. 
NW of NE 


"Various." 
See fauna! list. 

GiDLET Quarry. 


6 . 


SE of SE . . 


See faunal list. 


6 


NE of SW... 


Do. 


7 




(Not relocated— not a fossil 


8 

fl 


Near middle of east half_. 
SE of SE.. 


(In No. 2)... 
300 


locality). 
See faunal list. 
Do. 


10 

11 


H mile south of north 

section lines. 
SWof SW 


(In No. 3)... 

4,350 

1,700. 

4,350 

(In No. 2, a 
few feet be- 
low Loc. 3) 

(In No. 3)... 

1,250 

1,400 

3,500 

(In No. 3)... 

(In No. 3)... 

(In No. 3).., 

(In No. 3)... 

1,350 

800. 


Mammal fragments. 
See faunal list. 


12. . 


SE- 


Do. 


13 


SWof SE 


Do. 


14. 


Same as Loo. 3 


Mammal and other frag- 


15 


NE of SW 


ments. 
See faunal list. 


16 


NE of SW 


Invertebrates and mammal 


17... 


SE of NE 


fragments. 
Invertebrates. 


18 . 


NWofSE... . 


See faunal list. 


19 


NEofNE 


Mammal and other frag- 


20 


NE of NE.. 


ments. 
Invertebrates and Claenodon 


21 




{fide Silberling). 
(Not relocated.) Inverte- 


22 


SWof SW.... 


brates. 
Plants. 


23 

24 


Near middle of east half. 
NW of NW 


Footprints, plants. 
See faunal list. 


25 


SW of SE 


800 


Do. 


26... 




L.\NCE 

1,750 

1.750 

(In No. 2)... 
850 ... . 


(Not relocated.) Plants. 


27 


NEofSE 


See faunal list. 


28 


NWof SW 


Do. 


29 


NWof NW 


Invertebrates. 


30 . 


NW... 


Champsosaur and mammal 


31 




Lance 

(In No. 3)... 

•>,250 

Kootenai.. 
(In No. 3).-. 

2,250 

(In No. 3)... 

?,250 

1,350 

2,300 

2,325 

2,250 

2,250 


fragments. 
(Not relocated.) Invert©* 


32 




brates. 
Do. 


33 


SW 


Invertebrates. 


34 




(Not relocated.) Plants. 


35 


NE ofSE 


Plants. 


36 

37. 


Near center of north line. 
NE of SE 


See "Princeton Localities." 
Plants, invertebrates. 


38 -. 


SE of NW 


See "Princeton Localities." 


39 


SErf SE 


See faunal list. 


40 


SWof NW 


See "Princeton Localities." 


41 


SEof NW 


Do. 


42 


NEof NW 


Do. 


43 


NWof NW 


Do. 



44 BULLETIX 16 9, UNITED STATES XATIONAL MUSEUM 

Table 2. — Serial list of localities, Crazy Mountain Field, Mont. — Continued 



No. 


Quarter 


Section 


Town- 
ship 
North 


Range 

East 


Feet above 
base of Fort 
Union No. 1 


Remarks 


44 


SE cf SE 


7 

17 
24 
10 
25 
23 

9 

24 
23 

14 
23 
29 
13 

17 
20 

20 
19 
1 
7 

18 
34 
26 
14 
10 

20 
18 
31 
36 
12 

34 
15 
5 

11 

32 

26 
10 

14 

23 

11 


5 
5 
5 
5 
5 
5 
3 

4 

5 
4 
5 
5 
5 
5 
5 

5 
5 
5 
5 
5 
6 
6 
5 
5 

5 
5 
6 
6 

5 

6 
5 
4 

5 

5 
6 
5 

5 

6 

4 


15 

15 
14 
14 
14 
14 
15 

15 
15 

15 
15 
15 
14 
15 
15 

15 
15 
14 
15 
15 
16 
16 
13 
13 

15 
15 
15 
14 
14 

16 
15 
16 

15 

15 
16 
13 

13 

15 

15 


2,500 

2,250 

(In No. 3)— 
(In No. 3).„ 
(In No. 3)..- 

4,350 

800 


See "Princeton Localities." 


45. 

46 


SEof SWof SW 

NWofNW 


Do. 

Invertebrates. 


47 


NE of NE 


Plants. 


48 .. 


NE 


Do. 


49 .. 


NW of NW 


Mammal fragments. 


50 


Near middle of south 

halt. 
SW 


See faunal list. 


51 


575 


Do. 


52 


NW of NE 


1,150 

1,3.50 

1,200... 

2,300 

3,350 

2,250 

2,250 

2,250 

2,275 

(In No. 3)... 

2,850 

2,850 

1,250 

35. 


Do. 


53 

54 


NWof NWofNW 

NWof NE.... - 


Do. 
Do. 


55 .. 


NW 


Invertebrates. 


56 


SEofNW 


ScAERiTT Quarry. 


57 


SWofSE 


See "Princeton Localities." 


58 

59 


Near center line in north 

half. 
East half 


Invertebrates. 

See "Princeton Localities." 


60 

61 


SEof NWof SW 

SE - 


Do. 
Do. 


62 


SW of SW 


Do. 


63 


NW 


Do. 


64 


SW 


Mammal fragments. 


65 . 


SE of SW... 


See faunal list. 


66 


SW 


5,100 

5,000 

2,250 

2,850 

(In No. 3)... 
(In No. 3).-. 
(In No. 3).._ 

500 


Do. 


67... . 


SE of SE 


Plants, invertebrates, rep- 


68 

69 


Near center of north line . 
SW 


tiles. 
See "Princeton Localities." 
Do. 


70 

71 . 


Near middle of east half. 
SE of SE. 


See faunal list. 
Mammal fragments. 


72 

73. .. 


Near middle of north 

half. 
NE of SW 


See "Princeton Localities." 
See faunal list. 


74 


NEofNE 


1,350 

(Lower part 

of No. 2). 
(Lower part 

of No. 2). 
(In No. 3)._- 

200- -- 

(High in No. 

3). 
(High in No. 

3). 
800 .- 


Fish. 


75 


SW - 


Mammal fragments. 


76 


SWofSE 


Do. 


77 


NE 


Do. 


78 


SWof SW 


See faunal list. 


79 


NE 


Champsosaur. 


80.. 


NE 


Plants. 


81 


Near middle line in 

south half. 
SWof SWof SW 


See faunal list 


82 


1,350 


Do. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



45- 



Section 10: Locs. 67, 79. 



INDEX TO LOCALITIES BY SECTION NUMBERS 
Township 5 North, Range 13 East 

Section 14: Locs. 66, 80. 
Township 5 North, Range 14 East 



Section 1: Loc. 61. 
Section 9: Loc. 15. 
Section 10: Loc. 47. 
Section 12: Loc. 72. 
Section 13: Locs. 20, 56, 
Section 14: Loc. 18. 



Section 2: Loc. 24. 



Section 14: Locs. 53, 82. 
Section 15: Loc. 39. 



Section 15: Loc. 19. 
Sections 15-16: Loc. 10. 
Section 22: Loc. 13. 
Section 23: Locs. 11, 49. 
Section 24: Loc. 46. 
Section 25: Loc. 48. 

Township 6 North, Range 14 East 

Section 36: Loc. 71. 

Township 3 North, Range 15 East 

Section 9: Loc. 50. 

Township 4 North, Range 15 East 

Section 24: Loc. 51. 
Section 35: Loc. 25. 

Township 5 North, Range 15 East 



Section 7: Locs. 44, 62. 

Sections 11-14: Locs. 3, 14. 

Section 11: Loc. 76. 

Section 15: Locs. 17, 74. 

Section 16: Loc. 21. 

Section 17: Locs. 33, 38, 45, 57. 

Section 18: Locs. 63, 69. 



Section 19: Loc. 60. 

Section 20: Locs. 36, 42, 43, 68, 59, 68, 

Section 23: Locs. 4, 52, 54. 

Section 25: Loc. 32. 

Section 29: Locs. 40, 41, 55. 

Section 32: Loc. 77. 



Township 6 North, Range 15 East 



Section 23: Locs. 8, 81. 
Section 26: Loc. 31. 
Section 29: Locs. 28, 29. 
Section 30: Locs. 12, 27, 30. 



Section 31: Loc. 70. 
Section 34: Loc. 16. 
Section 35: Loc. 9. 



Section 5: Loc. 75. 



Section 4: Loc. 1. 



Section 25: Loc. 7. 
Section 26: Locs. 65, 78. 
Section 31: Loc. 26. 



Township 4 North, Range 16 East 

Section 7: Loc. 2. 

Township 5 North, Range 16 East 

Section 8: Loc. 23. 

Township 6 North, Range 16 East 



Section 33: Locs. 5, 35, 37. 
Section 34: Locs. 6, 16, 22, 64, 73. 



Township 7 North, Range 16 East 
Section 36: Loc. 34. 



46 



BULLETIN 16 9, UNITED STATES NATIONAL MUSEU^^I 



FAUNAL SUCCESSION AND CORRELATION 

COMBINED FAUNAL LIST 

Table 3 lists all the genera and species of mammals so far identified 
in this field, with the approximate level in the Fort Union series at 
which each is known to occur. The only omissions are a few speci- 
mens of uncertain level. They include no forms not otherv.-ise recorded 
here but might have extended the vertical distribution were their 
horizons accurately known. 

The list incidentally emphasizes the extraordinary richness of this 
field and its known faunas. It shows the presence of 51 genera (5 
tentatively identified, but different from the 46 definitely known) and 
79 species (15 tentatively identified or now nameless, but different 
from the 64 definitely known and named). The field is richer in 
variety of fossil mammals than the Puerco and Torrejon together, 
indeed almost as rich as all the other North American Paleocene 
combined. 

The figures given for each column are the approximate stratigraphic 
levels in feet above the base of the Fort Union No. 1. In the 575 
column, fossils from Loc. 51 are listed. The 800 column mcludes 
Locs. 24, 25, 50, and 81. The 1,150-1,200 column includes Locs. 
5, 6, and 54 and the Gidley Quarry. The 1,265 is the Silberling 
Quarry. The 1,350 includes Locs. 35, 53, and 82, and 1,700-1,750 
is Locs. 12, 27, and 28. The "Princeton localities" are included in 
the 2,250-2,350 column, and Loc. 18 and the Scarritt Quarry in the 
3,350-3,500 column. The last column, 4,350, is for Locs. 11 and 13. 

Table 3. — Combined faunal list, Crazy Mountain Field, Mont. 



Species 



No. 1 



(At 

level 

shown) 



No. 2 



575 
feet 



800 
feet 



1,150- 
1,200 
feet 



1,265 
feet 



No. 3 



1,350 
feet 



1,700- 
1,7.50 
feet 



2.250- 
2,350 
feet 



3,350- 
3,500 
feet 



4.350 
feet 



PtUodus montanus 

fPtilodus douglassi 

f PtUodus gidleyi 

fPtilodus sinclairi.. 

PtUodus sp.- 

fEciypodus grangeri.. 

tEctypodus Tusselli 

fEctypodus sUberlingi 

Ectypodus hunleri 

fParectypodus jepseni 

Eucosmodon sparsus 

Gelastops parcus 

Prodiacodon concoTdiarcensis. 

Leptacodon tadae 

Leptacodon munusculum 

Leptacodon cf . tener 



35 



FORT UNIOX OF CRAZY MOUNTAIN FIELD, MONT. 4T 

Table 3. — Combined faunal list, Crazy Mountain Field, Mont. — Continued 





No. 1 


No. 2 


No. 3 


Species 


(At 

level 

shown) 


575 
feet 


800 
feet 


1,150- 
1,200 
feet 


1,265 
feet 


1,3.50 
feet 


1,700- 
1,750 
feet 


2,250- 
2,350 
feet 


3,350- 
3.500 
feet 


4,350 
feet 




Feet 






X 

X 


X 








X 
X 

X 

X 
X 




Siilpnodon simplicidens 










Bessoecetor dHuculi .. 




















Cf. Palaeosinopa sp 


























X 


X 
X 


X 
X 










Eudae/nontma cuapidata 








Etpidophorus palratus 








X 


Elpidophorus minor . 










X 
X 


















X 






' 








Pronothodectcs malthewi 








X 












PUsiadapis anceps .. 










Ptesiadapis rex .. . 


















X 










X 










X 














ParomoTnys maturus 








X 
X 


X 










Paromomys depressidem 










Cf. Paromomys, genus and species 








X 


Palaechthon alticuspis 








X 
X 


X 








X 
































X 


X 




X 


X 




Cf. Conoryctes sp 










Psittacotherium muUifragum 










X 


X 




Claenodon montanensis 








X 
X 
X 




Claenodon silberlingi.. 










Claenodon latidens 












300 








Claenodon fferox 


X 


Claenodon sp 








X 
X 


X 




Deulerogonodon montanus.. 






X 
X 












Prothri/placodon furens 








Prothryptacodon ffurens 






X 










X 




200 
















X 
X 








Metachriacus punitor 








X 


X 
X 

X 
X 

X 

X 

X 
X 










Metachriacus provocator 




X 
X 


X 










Spanoxyodon latruncului 






X 
X 














Mimotricentes f latidens 






X 






500 
300 


X 




fMimolricentes sp. ... 


X 


X 
X 

X 
X 
X 




















X 


X 




















Ellipsodon aguilonius 




X 












Litaletes disjunctus 




X 




X 













48 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

Table 3. — Combined faunal list, Crazy Mountain Field, Mont. — Continued 





No. 1 


No. 2 


No. 3 


Species 


(At 

level 

shown) 


575 
feet 


800 
feet 


1,150- 
1,200 
feet 


l,2fi5 
feet 


1,350 
feet 


1,700- 
1,750 
feet 


2,250- 
2,3.50 
feet 


3,350- 
3,500 
feet 


4,350 
feet 


Litomylus dissentaneus . 


Fed 






X 
X 














Haplaletes disceptairix 










Cf. Haplaktes sp 








X 


Litolestes notimmus 


















X 
X 




Telradaenodon symbolicus 






X 


X 


X 


X 








Tetraclaenodon cf. symbolicus 


300 


X 




Telradaenodon cf. puercensis 




Telradaenodon spp 








X 


Gidleyina monianensis 
















X 




fOidleyina silberlingi. 














X 




f Gidleyina superior 














X 


fGidleyiva sp 
















X 
X 

X 


X 
X 




Coriphagus montanus... 








X 

X 
X 
X 


X 




X 
X 




Anisonchu) sedorius... 




X 


X 




Pantolambda intermedius 






X 




fPanlolambda sp 










Pantolambdids undetermined- 

























FAUNAL SUCCESSION 

The No. 1 beds have yielded only fPtilodus sinclairi from near the 
base; Claenodon vecordensis, Chriacus pugnax, fMimotricentes sp., and 
Tetraclaenodon fsymbolicus from near the middle part; and Mimotri- 
centes angustidens from the top. The first and last of these forms are 
inseparable from species occurring well up into the No. 2, and so is 
Tetraclaenodon fsymhoUcus. Claenodon vecordensis and Chriacus 
pugnax are distinct species but cannot be considered to be clearly 
ancestral to anything known from the No. 2. The evidence is inade- 
quate to demonstrate either occurrence or absence of distinct faunal 
advance within the No. 1-No. 2 series. It does suggest, however, 
that such advance must have been relatively slight and that it was 
probably of less than generic rank, if it occm'rcd. The data definitely, 
if not altogether conclusively, oppose the hypothesis that the difference 
between No. 1 and No. 2 faunas can have been as great as between 
Puerco and Torre j on. 

Within the No. 2 beds the first important point is that the Gidley 
and Silberling Quarry faunas are identical in degree of evolutionary 
progress and show no significant difference in age despite a small 
difference in level, about 65 feet. There are 23 species definitely- 
identified in the Silberling Quarry. Seventeen of these also occur in 
the Gidley Quarry and, as shown in the systematic descriptions, these 
suggest no difference, even of less than specific rank, between the 
forms in the two quarries. Four Silberling Quarry species do not 
occur in the Gidley Quarry but do occur at lower levels, so that their 



rOKT UXIOX OF CRAZY MOUisTAIX FIELD, MONT. 49 

absence in the Gidley Quarry is not due to time differences but to 
facies or accidents of discovery. These species are Eucosmodon 
sparsus,^'^ Mimotricentes angustidens, Didymictis haydenianus,^^ and 
Tetraclaenodon symbolicus. Only two species, Psittacotherium multi- 
fragum and Elpidophorus minor, known only from one specimen each, 
are confined to the Silberling Quarry, and there can be no doubt that 
this is the result of chance. The Gidley and Silberling Quarry 
faunas are, then, a unit as far as appreciable differences in time are 
concerned. 

The 575-foot level is represented by eight definitely identified 
species, of which seven also occur in the Gidley or Silberling Quarries 
or both, and the other, Metachriacus provocator, reappears at the 
800-foot level. The 800-foot localities have 10 definitely identified 
species, 8 of which also occur in the Gidley or Silberhng Quarries or 
both, while Deuterogonodon monianus is confined to this level and 
Metachriacus provocator appears also 225 feet lower. All the material 
of Deuterogonodon monianus is from a single locality, and it must be 
considered as a sporadic and chance occurrence with no probable 
validity as an index of time relationship, particularly as no probable 
or possible ancestral or descendent forms occur in this field. The 
distribution of Metachriacus provocator is pecuhar. It is relatively 
very abundant at No. 2 levels below^ the Gidley Quarry, being the 
only species that occurs at all these locahties (except for Loc. 52, 
which is only 50 feet below the Gidley Quarry and must be considered 
as at essentially the same level) . At the Gidlej' and Silberling Quarry- 
levels it has not been found, but an allied species, M. punitor, is 
present and fairly commxon. M. provocator is the larger and in some 
other respects probably the more speciaHzed of the two species, 
despite its earUer appearance. Thus the relationship is not that of 
ancestor to descendant, and no temporal difference is demonstrated. 
The facies of these earlier locahties are demonstrably quite different 
from those of the quarries, and the most reasonable conclusion is 
that the distribution of the two species of Metachriacus is conditioned 
by facies and not by time. 

It thus appears that the whole Fort Union No. 2 shows no probable 
significant faunal advance and that it forms a unit as far as time and 
correlation are concerned. 

It is particularly unfortunate that the three lower fossil zones of 
the No. 3 beds are represented by few and poor specimens, for this 
is a crucial point in the sequence, probably covering (as shown under 
* 'Correlation") the transition from Middle to Upper Paleocene. The 
lowest level, 1,350 feet, yields Claenodon fferox, Tetraclaenodon cf. 
puercensis, and indeterminable pantolambdids. The latter have no 
particular importance. Claenodon fjerox occurs almost throughout 

" These probably are present in unprepared Gidley Quarry material. 



50 BULLETIN 16 9, UXITED STATES NATIONAL MUSEUM 

the No. 3 beds but is not recorded in the No. 2 where there are smaller 
and probably somewhat more primitive species of the same genus. 
The Tetradaenodon is not distinguishable from one in the Gidley 
Quarry, or from fragmentary specimens from high in the No. 3. The 
1,700-foot level has cf. Conoryctes sp., fGidleyina silberlingi, Anisonchus 
sectorius, and pantolambdids. The first and last have no apparent 
significance for this discussion. fGidleyina silberlingi marks the first 
(probable) appearance of that genus, which seems to be confined to 
the No. 3 and more progressive than any tiling in the No. 2. Anison- 
chus sectorius ranges throughout the No. 2 and far up into the No. 3. 

The 2,250 to 2,350 levels (chiefly "Princeton locahties") yield 
Claenodon ?Jerox, Gidleyina montanensis and G. spp., Anisonchus 
sectorius, and pantolambdids that are undetermined but are distinct 
from anything in the No. 2 beds. Loc. 15, which is somewhere in the 
lower No. 3 although not determined exactly as to level, yields an 
ally of Paromomys not demonstrably distinct from the No. 2 repre- 
sentation of that group. 

These lower No. 3 beds as a whole appear to be characterized by 
the survival of some genera, including Claenodon, Tetradaenodon^ 
Anisonchus, and perhaps Paromonnys and Conoryctes, and of at least 
one species, Anisonchus sectorius, from the No. 2 beds, and by the 
appearance of a distinctive advanced species, Claenodon fjerox, and 
a similarly distinctive and relatively specialized genus, Gidleyina. 
These two latter may not be real cases of faunal advance, for it is 
possible that these animals were already present in No. 2 time despite 
the lack of discovery, yet it seems tentatively acceptable to consider 
them as suggestive of some slight faunal progress. The data are too 
scanty for any definitive conclusion, but the indications are that these 
strata have a transitional fauna between that of the No. 2 beds and 
that of the Scarritt Quarry, about 1,000 feet above these lower No. 3 
levels. 

The Scarritt Quarry, at about 3,350 feet, provides good data and 
for the first time shows decisive and incontrovertible evidence of 
faunal change in the series. Ectypodus hunteri is evidently related 
to some species from the Gidley Quarry but is certainly distinct and 
probably of later aspect, and the same is true of Leptacodon cf. tener. 
Bessoecetor thomsoni also has a Gidley Quarry ally but is probably not 
a descendant of the latter. The relative degree of specialization is 
not clear. Elpidophorus patratus is more speciaHzed than its fore- 
runner ?E. minor in the Silberling Quarry. Plesiadapis anceps is 
very primitive in its genus yet is more advanced than Pronothodectes, 
from which it could well have been derived. The relation between 
Carpodaptes in the Scarritt Quarry and Elphidotarsius in the Gidley 
Quarry is closely analogous to that between Plesiadapis and Pronotho- 
dectes. Phenacolemur has no definitely recognizable ancestor in the 



FORT UI^ION OF CRAZY MOUNTAIN FIELD, MONT. 51 

lower beds but is a progressive and specialized form. Litolestes is 
allied to Hajdaletes and might have been, but probably was not, 
derived from the latter (but surely not from the known species). In 
any case, it is a distinctive genus abundant here and unknown in the 
No. 2 beds. Tetraclaenodon occurs in both series, and the species are 
not well enough known for useful comparison. Finally, Anisonchus 
sectorius, which ranges throughout the No. 2, is also present here 
(not in the Scarritt Quarry but at Loc. 18, which is not appreciably 
different in level). 

If we discount the influence of facies and chance as far as possible, 
it then seems clear that there is definite faunal advance from the 
Gidley and Silberling Quarry levels to that of the Scarritt Quarry, 
that this advance is in some cases of generic rank {Pronothodedes- 
Plesiadapis and Elphidotarsius-Carpodaptes) but in others only 
specific (probably in the genera Edypodus, Leptacodon, Bessoecetor, 
Elpidophorus , and Tetradaenodon) and in part of even less degree 
(Anisonchus sedorius)}^ 

The progressive difference in the two faunas compared is real, but 
it is not very marked, much less than would be expected from a 
difference in level of some 2,000 feet. As nearly as such an imperfect 
parallel can be drawn, the difference seems to be definitely less than 
that between the Torrejon and the Tiffany and probably not much 
greater than between the Tiffany and Clark Fork. 

The highest faunal level, 4,350 feet, has provided Uttle good evidence 
bearing on this discussion. Plesiadapis rex may be more progressive 
than P. anceps but is not definitely shown to be so. The Paromomys- 
hke form is too poorly known for useful comparison. Tetradaenodon 
still occurs at the higher level and so probably does Gidleyina, their 
degree of advance, if any, over comparable forms lower in the No. 3 
beds not being clear, 

Claenodon fjerox still occurs here and seems to be quite as in the 
lower No. 3, although the material is scanty. Thryptacodon, identi- 
fied with much probability but not certainty, is progressive over 
Prothryptacodon of the No. 2, but the intermediate stages in the lower 
No. 3 are unlvnown. An ally of Haplaletes here is too poorly known 
to give reliable evidence. Elpidophorus, probably patratus, carries 
through from the Scarritt Quarry level. The data are too inadequate 
to say that there is no advance over the Scarritt Quarry, or indeed 
over the lower No. 3, but they suggest that the difference will probably 
prove to be slight if it exists at all. 

'3 The tremendous vertical range of Anisonchus sectorius in this field, nearly 3,000 feet, is extraordinary. 
This species and to still greater degree this genus are of unusually wide geographic range in the Paleocene, 
the species known from New Mexico to Montana and the genus also in Louisiana, and also are unusually 
conservative— the genus is one of the two or three that pass through from Puerco to Torrejon in New Mexico. 



52 BULLETIN 169, UNITED STATES NATIOX.AL MUSEUM 

CORRELATION OP MAMMALIAN FAUNAS 

Data are not at hand for any exact correlation of the No. 1 beds. 
Of then- mammals IPtilodus sinclairi, identified here with some prob- 
ability, is a No. 2 species. Claenodon is typically a Middle Paleocene 
genus, ranging in this field into the Upper Paleocene. Chriacus is a 
very long-lived genus. Lower Paleocene to Lower Eocene, and is here 
rather dubious but apparently of more progressive aspect than it& 
Lower Paleocene allies. Alimotricentes is otherwise known only in the 
Middle Paleocene of tliis field, and M. angustidens (which, however, 
is known only from the highest No. 1 beds) ranges to the top of the 
No. 2. Tetradaenodon is typically Middle Paleocene, perhaps ranging 
into earliest Upper Paleocene in this field, and the species may be the 
same as in the No. 2. As identified by Russell (personal communica- 
tion), invertebrates from immediately below the No. 1 beds, or perhaps 
in their base, are definitely of Paleocene aspect, and most of his com- 
parisons are closely with Middle to Upper Paleocene forms. On the 
whole the scanty evidence favors reference of the No. 1 beds to the 
Middle Paleocene, and none of it definitely suggests or warrants 
reference to the Lower Paleocene. The physical stratigraphic evi- 
dence, while even less decisive, is also consistent with belief that the 
No. 1 beds are not markedly different from the No. 2 in age. Nothing 
suggests or justifies correlation with the Puerco. 

As already shown, the fauna of the No. 2 beds is a unit as far as 
correlation is concerned. From his first discovery (Locs. 5 and 6), 
Douglass (1902) already recognized equivalence to the Torrejon. 
Matthew (1914) accepted this fauna as of the same age as that of 
the Torrejon.^* Gidley (1909, p. 616, footnote, apparently not else- 
where explicitly stated, but liis definitive opinion) considered it "about 
equivalent to ... or perhaps somewhat older than the Torrejon." 
The detailed evidence of the mammalian fauna is as follows: 

Ptilodus: A Middle Paleocene genus, P. montanus very near P. mediaevus of the 

Torrejon. 
Eciypodus 1 [TypicaUy Upper Paleocene genera, but species here quite distinc- 
Parectypodus]' { tive and generic assignments not certain. 
Eucosmodon: Forms indistinguishable generically on the basis of similar material 

range through the Paleocene. 
Gelastops: Probably allied to, but distinct from, Didelphodus of the Lower Eocene. 

Probably allied to but less specialized than Acmeodon of the Torrejon. 
Prodiacodon: Middle Paleocene genus, identification here not certain and species 

highly distinctive. 
Leptacodon: Genus otherwise Upper Paleocene, species distinctive. 
Myrmecohoides: Unknown elsewhere, no value in close correlation. 
Stilpnodon: This genus and its family too imperfectly known for close comparisons. 
Bessoecetor: Otherwise known only in the No. 3 beds in this field, allied to the 

typically Lower Eocene Palaeosinopa, but more primitive. 

1* Uis correlation chart, fig. 2, seems to correlate it with the Puerco, but his text shows that this was not 
intended. 



FORT UNION OF CEAZY MOUNTAIN FIELD, MONT. 53^ 

Aphronorus: Allied to Pentacodon of the Torre j on but apparently more primitive. 
Eudaemonema: Allied to Mixodectes in the Torrejon and (perhaps more distantly) 

to other genera in Upper Paleocene and Lower Eocene, more primitive than 

any of these allies in some respects, but not on the same line of descent as- 

any of them. 
Elpidophorus: An Upper Paleocene genus but here with a distinctive primitive 

species, which may weU prove generically separable. 
Picrodus: Probably allied to Zanyderis of the Upper Paleocene, relative degree 

of specialization not determinable. 
Pronothodedes: Allied to Plesiadapis of the Upper Paleocene but distinctly more 

primitive. 
Elphidotarsius: Allied to Carpodaptes and Carpolestes of the Upper Paleocene but 

distinctly more primitive than either. 

7-, 7 7., [Generally primitive genera, but exact lines of descent not clear 

Palaechthon } \ ^ / . . ... 

„ , ,,, enough for more precise use m correlation. 

Palenochtha] 

Conorydes: Genus otherwise Middle Paleocene as far as definitely known, species 

imperfectly represented but indistinguishable from C. comma of the Torrejon. 
Psittacoiherium: Genus otherwise certainly known only in Middle Paleocene^ 

species indistinguishable from P. multifragum of the Torrejon. 
Claenodon: Genus otherwise chiefly Middle Paleocene but extending into Upper 

Paleocene in this field, species more primitive than that commonest in. 

Torrejon, more comparable to but perhaps slightly more primitive than the 

second Torrejon species. 
D enter ogonodon: A distinctive genus not known elsewhere, perhaps especially 

allied to, but if so distinctly more advanced than, Proto§onodon of the Puerco. 
Proihryplacodon: Allied to Thryptacodon, Upper Paleocene and Lower Eocene,, 

but more primitive. 
Metachriacus] j Genera, unknown elsewhere, of Paleocene aspect but not more 
Spanoxyodonjl closely useful in correlation. 
Mimotricentes: Perhaps especially allied to Tricentes, Middle Paleocene, and if so 

slightly more primitive, but probably on a diflFerent line of descent. 
Didymidis: Genus Middle Paleocene to Lower Eocene, relationship of two species 

not clear enough for more exact correlation, but a third indistinguishable 

from D. haydenianus of the Torrejon. 
Ididopappus: Unknown elsewhere, perhaps especially allied to Viverravus of the 

Eocene, but if so more primitive. 
Dissacus: Genus Middle Paleocene to Lower Eocene, species not identifiable. 
Ellipsodon: Genus otherwise only positively identified in Middle Eocene, species 

close to E. acolytus, Torrejon, perhaps slightly more advanced or on different 

line of descent. 
Litaletes | [ Genera unknown elsewhere, general aspect Paleocene, perhaps 
Litomylus \ \ rather more Middle Paleocene, but not exactly determinable as 
Haplaletes] [ to evolutionary position. 
Telradaeiiodoit: Genus typically Middle Paleocene, probably reaching Upper 

Paleocene in this field, two species close to those from Torrejon, one of them 

indistinguishable. 
Coriphagus: Genus otherwise only in Torrejon, species closely allied. 
Anisonchus: Genus Lower and Middle Paleocene, also Upper Paleocene in this 

field only, species same as in Torrejon, but probably also reaches Upper 

Paleocene here. 
Pantolamhda: Genus certainly identified only in Middle Paleocene, species allied 

to those of Torrejon. 



54 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

In resume, there are 13 genera all of Paleocene aspect but con- 
fined to this fauna and of little use in exact correlation. Of the eight 
■other genera confined to this fauna, four have their closest allies 
in the Torre j on and four have their closest known allies in the Upper 
Paleocene, but three of these here appear to be distinctly more primi- 
tive than their Upper Paleocene relatives. Eight genera are other- 
wise typical of the Torrejon, and these here include two species 
indistinguishable from those of the Torrejon. The other species of 
these genera are in most cases closel}^ allied to those of the Torrejon, 
mostly without definite evidence of being more or less advanced, 
but one may be less and one may be more specialized than the most 
.comparable Torrejon species. Four genera are common to this fauna 
•and to that of the Torrejon, but they also appear in later beds. Their 
species are here generally closer to the Torrejon species and in two 
cases appear to be identical. Two genera probably range nearly 
,or quite throughout the Paleocene, one of them here represented 
by a typically Torrejon species, but one that does range into some- 
what later beds. Five of the genera are otherwise known only in 
Upper Paleocene (in some cases also ranging into later) beds, but in 
each case the species here present is decidedly distinctive, and in no 
«ase is a Middle Paleocene ancestor or close ally otherwise known. 

This evidence conclusively proves the fauna to belong to the 
Middle Paleocene and to be close to the Torrejon in age. It does 
not preclude a slight difference in age from the Torrejon, but dif- 
ferences of facies and geographic position are adequate to explain the 
faunal distinction without supposing the age to be different, and if 
the age is slightl}^ different they obscure the evidence for this. There 
is nothing suggestive of the Puerco. There is a greater resemblance 
to the Upper Paleocene than is shown by the Torrejon fauna, but the 
evidence suggests that this is largely or wholly due to the discovery 
in this place and facies of forerunners of later groups not themselves 
really later here than the Torrejon. 

The onl> other very closely correlatable horizon is that of the 
Scarritt Quarry. The correlation has been discussed elsewhere 
(Simpson, 1936b), where it was shown that the quarry fauna itself 
is very close to that of the Tiffany in age but may be slightly earlier. 
From a more general point of view, there is some suggestive but 
inconclusive evidence strengthening the probability of slightly earlier 
age for this than for the principal Tiffany horizon. The probable 
occurrence of Tetraclaenodon at an even higher level, replaced in 
the Tiffany and all later beds by the more advanced and possibly 
descendant genus Phenacodus, weights the evidence in this direction, 
as does also the occurrence at about this level of a specimen indis- 
tinguishable from Anisonchus sedorius, a Torrejon species. The 
.occurrence of Claenodon indistinguishable from the Torrejon C. ferox 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT 



55 



far up into the No. 3, even higher than the Scarritt Quarry, is less 
dependable but suggests the same conclusion. It is also suggestive 
that the age difference between the Gidley and Silberling Quarry 
faunas, which are very close to the Torrejon in age, and that of the 
Scarritt Quarry appears to be less pronounced than the age difference 
between the Torrejon and the Tiffany. 

The Scarritt Quarry and equivalent levels may be correlated with 
the Tiffany, with the reservation that it is possibly a little earlier, 
and may be placed in the earUest Upper Paleocene. The highest 
faunal level, that of Locs, 11 and 13, is likewise surely Upper Paleo- 
cene, probably about Tiffany. 

The lower levels in the No. 3 cannot be well correlated on present 
data. They are bounded by Torrejon and (probably early) Tiffany 
equivalents. There is some slight evidence that they are in fact 
transitional between these two and represent most of the gap in 
time known to exist between Torrejon and Tiffany, rather than being 
more definitely associated with one or the other. If there is a dis- 
tinct faunal break in this series, it would be logical to look for it at 
the most obvious change in sedimentation, at the base of the No. 
3. The scanty fossil evidence does not warrant such a positive 
conclusion. The only known elements in the basal No. 3 that look 
toward the later faunules are Claenodon fjerox of little or no value, 
since this is, in fact, a typical Torrejon species, and Gidleyina, which 
is more suggestive but in itself far from conclusive. 





Colorado-New 

Mexico: 
San Juan Basin 


Wyoming: 
Bighorn Basin 


Montana: 
Crazy Mountain Field 


Paleocene 


(No mammals 
known) 


Clark Fork 


(No mammals 
known) 

? 


Tiffany 


"Tiffany-Bear 

Creek" 

(Princeton Quarry) i 


) Scarritt Mel- 
Quarry ville 
? 


(Faunal break) 


(Faunal break) 


Torrejon 


"Torrejon" i 


Gidlev T I 
)QuarVy ^^^^ 

? 


(Faunal break) 


(Faunal break) 


Bear 

(Age uncertain) 


Puerco 


"Puerco" 1 


Cretaceous 


(Unconformity) 


Lance 


Hell Creek 



• Dr. Jepsen has not yet applied valid stratigraphic names to these levels, distinguished by him. 
119212—37 5 



56 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

The kno^vll faunas of this field thus seem to cover most of or all 
the Middle Paleocene and to continue, probably without a marked 
break, into the early Upper Paleocene. There are here at least 
2,000 feet of sediments of about the same type above the highest 
level with identified mammals, and sediments of somewhat different 
character in contiguous areas might raise this figure to as much as 
4,000 feet. These beds doubtless represent most of or all the con- 
siderable span of later Upper Paleocene time not represented by 
faunas here, and they may well run into the true Eocene. 

The tentative arrangement based on these correlations is summed 
up in the diagram on page 55. 

Such a chart is necessarily excessively simplified, so that it does not 
adequately represent abundant and exact evidence where this is 
available; at the same time it must be explicit, so that in places it does 
not reveal the extent of uncertainty and lack of evidence. It is a 
correlation of strata by their known faunas, never entirely coextensive 
with the strata themselves. The "faunal breaks" listed definitely 
imply intervals of time not represented by known faunas, but it does 
not follow that strata of these ages are necessarily lacking in the region 
in question. The same is true of the parts outside the known distri- 
bution of faunas that are labeled "no mammals known." 

ECOLOGY 

NOTES ON THE NONMAMMALIAN BIOTA 

Despite the abundance of nonmammalian fossils in the field and 
the existence of good collections made by Silberling and others, this 
part of the biota has not been adequately studied for this area. It 
is beyond the scope of the present work to include any critical exami- 
nation of the material or to attempt complete floral and faunal lists, 
nor has it seemed necessary to delay publication until such special 
studies could be made. In the present section a few previous records 
are mentioned, and beyond this the only purpose is to suggest the 
broad outlines or general character of the biotic background of the 
mammalian faunas. 

Plants. — A number of small collections of leaves have been made in 
this field, but as far as I laiow no attempt to collect and to classify 
its whole flora has been made. Ejiowlton (1902) has published a 
special note on one small collection, and several other species are listed 
incidentally in the literature. 

Knowlton (1909, p. 194) listed a few plants from the "lower mem- 
ber of the Fort Union" (by which he usually means the Hell Creek or 
La.nce), 1,000 feet below the top. As it is not clear what he considered 
"the top", this is not explicit. He states that they were "about 1,200 
feet below the small mammals now being studied by Mr. Gidley", 
which probably means the Silberling Quarry and would (by my esti- 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 57 

mate) place the plants near the top of the Bear. They are said to be 
from sec. 29, T. 6 N., R. 16 E., a section that is mainly on the Bear 
but includes a small area of No. 1. The identifications are: 

Salix sp. Aralia notata. 

Populus aynhlyrhyncha. Leguminosiies arachioides. 

Populus cuneata. Vitis xantholithensis. 

Populus genetrix. Credneria daturaefolia. 

Populus daphnogenoides. Phyllites cupanoides. 

Populus sp. Carpites sp. 

These are all common Fort Union species. Knowlton has also re- 
ported them all as Lance (e. g., Knowlton, 1919), but on examining the 
evidence it is found that Vitis (or Ampelopsis) xantholithensis, Cred- 
neria daturaefolia, and Phyllites (or Pterospermites) cupanoides are 
true Fort Union species reported in the Lance only on the strength 
of this occurrence, and that there is also some question as to whether 
Aralia notata really occurs in the Cretaceous, whereas it is abundantly 
characteristic of the Fort Union. '^ In short, this is a Fort Union 
flora, which would be expected since it is probably from the Bear, 
w^hich may well be Paleocene or even properly Fort Union, or possibly 
from the Lebo, which everyone now agrees to be Fort Union. 

Other small collections more definitely from the Bear and older 
than any of the known mammals of this field are mentioned above. 

A collection surelv from the Lebo, "close under the massive gray 
sandstone of the Fort Union" (i. e., the base of the No. 3 beds), in 
"Sec. 15, T. 6 N., R. 15 E." (actually sec. 22, as later surveys have 
shown; sec. 15 includes only the very base of the Lebo), was made by 
Campbell, Stanton, Stone, and Calvert, and identified by Knowlton as 
follows (in Stone and Calvert, 1910, p. 755): 

Platanus haydenii. Sapindus grandifoliolus. 

Populus cuneata. Grewia obovata. 

Populus amhlyrhyncha. Greuiopsis platanifolia. 

These are all Fort Union species, and all occur in the Glendive 
region. The majority also occur in the Lance but are certainly in 
the Fort Union in this section. 

Knowlton (1902) described a small flora collected by W. H. Weed 
from "the sandstone series above the bend of the Sweet Grass, west 
of Porcupine Butte, Montana." This locality is in this field, at the 
extreme western edge of the mapped area, at a high horizon, far above 
any identified mam.mals. The following species were recorded: Glyp- 
tostrobus europaeus,^^ Onoclea sensibilis fossilis, Aralia Inotata, and 
Tilia iveedii. The last has not been recorded elsewhere, but the 
others are Fort Union (and questionably earlier) species, and Knowl- 

15 This incident casts further doubt on the supposed community of the Lance and Fort Union floras, for 
there are many other areas where beds probably or surely Paleocene and definitely post-Hell Creek have 
been arbitrarily called "Lance." 

'9 G. e. ungeri In the original list, but later emended by Knowlton to the form here given. 



58 BULLETIZSr 16 9, UNITED STATES NATIONAL, MUSEUM 

ton concludes that the beds are Fort Union. Incidentally this is 
some sUght evidence that these upper beds are still in the Paleocene, 
but this perhaps cannot be taken very seriously. 

It seems probable that the Fort Union flora of this field is closely 
similar to that of the Bull Mountain field (lists in Wooisey, Richards, 
and Lupton, 1917) and also to the very large and well-known flora 
of the Glendive area (lists and references in Knowlton, 1919), in short, 
that it is the typical, wide-ranging Fort Union flora, which seems to 
have shown little geographic or stratigraphic differentiation from 
Upper Cretaceous to Upper Paleocene and throughout the West. 
Leaves are found at almost all levels and throughout the field, although 
really well-preserved specimens can seldom be recovered. Specimens 
apparently of the handsome species Platanus nobilis were particularly 
noticeable in the sandstones stripped from above the bone layer 
in the Gidley Quarry. The general occurrence of leaves here and 
elsewhere in the field suggests that the whole region was heavily 
forested, chiefly by deciduous trees, during much of or all the Paleo- 
cene. It demonstrates the presence of a M^ell-developed arboreal 
habitat and of abundant food for browsing and frugivorous animals 
and suggests (but by no means proves) that the more open type of 
plains habitat was here relatively restricted or absent. 

Knowlton (1927, pp. 184-186) has summed up the Fort Union 
flora in general, and probably liis remarks apply in large measure to 
the i^lants of this field throughout Lebo and Melville time. About a 
dozen species of small ferns and the sensitive fern Onoclea are known, 
as well as horsetails, "a beautiful little selaginella", and abundant 
grasses and sedges. Only one palm, and that rare, is recorded. "It 
was, however, a very large-leaved fan-palm, showing that conditions 
were not altogether unfavorable." Conifers are abundant, with 
three sequoias, a yew, bald cypress, two or three pines, and an arbor- 
vitae that was particularly abundant. There is a rare ginkgo. The 
most conspicuous and abundant dicotyledonous trees were poplars, 
with leaves suggestive of the quaking aspen. Sycamores also were 
abundant, some with very large leaves. Viburnums were also very 
common and were "presumably small trees or shrubs, known at the 
present day as arrowwood, blacldiaw, tree cranberry, etc." There 
were also oak, alder, chestnut, hazelnut, maple, elm, magnolia, hick- 
ory, walnut, birch, beech, ampelopsis, bittersweet, and rare figs and 
laurels. 

Invertebrates. — Mollusks occur throughout the field and often in 
extraordinary abundance. The majority of them are fresh-water 
mussels and gastropods, although a few may be terrestrial snails. 
The common types are several dift'erent species each of "Z7mo", 
Viviparus, and Campeloma. A large collection from just below the 
Lebo has been hsted page 17. Dr. Russell has also identified the 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 59 

following from Loc. 24 (immediately above the mammals): Viviparus 
retusus, V. planolatere, and Lioplax nebrascensis; and the following 
from Loc. 67, high in the No. 3: INedionidus senectus, IN. s. declivis 
(type locality; Russell, 1934), Viviparus retusus, and V. cf. planolatere. 

(There are also large collections not adequately studied, nor is it 
necessary to discuss them here where only the general ecological 
aspect is in question.) 

Altogether, the invertebrates show that fresh water was abundantly 
present and thickly populated in this area throughout the deposition 
of the Fort Union. 

Fishes. — Fish remains are abundant in the field but usually very 
fragmentary. A few relatively good specimens have been recovered 
but have not yet been prepared or closely studied. Gar scales (Lep- 
isosteus sp.) are common at most surface localities and also occur in 
all three quarries. A stUl commoner fish in the quarries, seldom 
found on siu-face exposures, probably because of its more fragile 
character, appears to be an ally of, or to belong to, Stylomyleodon 
Russell, and Russell has already recorded its presence in this field 
(1928, p. 107). Specimens recently collected will add greatly to 
knowledge of this form. Despite the almost complete lack of associa- 
tion of mammal remains in the Gidley Quarry, it is the rule rather 
than the exception to find fishes, apparently mostly Stylomyleodon, 
represented by associated strings of vertebrae, despite the loose 
articulation of these, and not infrequently also with parts of the skull 
in association. 

Reptiles. — Champsosaur and crocodilian remains, generally too 
imperfect for close identification, are common at all levels. Isolated 
teeth suggest that Allognathosuchus was the common crocodilian. 
Champsosaurs occur up to at least 3,000 feet, and possibly more, 
above the base of the No. 3. Turtle remains are also common, but 
they also are usually too fragmentary for ready identification. Hay 
(1908, p. 498) has, however, described Aspideretes nassau from a 
specimen found by one of the Princeton parties in the No. 3 beds. 

Gilmore (1928b) has mentioned three fragmentary specimens of 
Peltosaurus sp. from the Fort Union No. 2 Silberling Quarry and has 
also named Harpagosaurus excedens, the type of which is from the 
same locality. Lizard remains are fairly common in both Silberling 
and Gidley Quarries, and it is probable that these animals were 
abundant in this region in the Middle Paleocene. 

MAMMALIAN FACIES 

The percentage composition of the principal No. 2 surface locali- 
ties, all near the same level and similar in facies, and of each of the 
three quarries is given in table 4 and shown graphically in figures 
1 and 2. 



60 



BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 




T^NIOOONTA' 



Figure 1.— Diagram showing the relative abundance of identifled individuals of the various orders an 
families of mammals in the National Museum collection from the Qidley Quarry. 



LOCALITIES 

24,25> 
S0,8t. 

ORDER 



GIDLEY SILBERLING SCARRITT 
QUARRY QUARRY QUARRY 



FAMILY 




(P.NYCTITHERIID-^ IN 
GIDLEY QUARRY LESS THAN 
y^ PERCENT.) 

Figure 2.— Comparison of relative abundance of families of mammals at various localities In the Crazy 
Mountain Field, Mont. Abundance is indicated for each locality by percentages of identifled individuals 
in the National Museum collection. Four Lebo surface localities (combined) and the three principal 
quarries are compared. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



61 



Table 4. — Composition {in percentages) of the principal No. 2 surface localities 
and of each of the three quarries, Crazy Mountain Field, Mont. 



Order and family 



Localities 
51, 24, 25, 
50, and 81. 


Oidley 
Quarry 


Pilberling 
Quarry 


9 


24 


44 


9 


24 


44 


1 


18 


12 





1 


2 





5 








(') 





1 


8 


7 





2 


2 





2 


2 














20 


4 





2 








(') 








18 


4 














(') 


4 





(') 


4 


53 


13 


19 


49 


7 


12 


4 


6 


5 





(') 


2 


37 


24 


18 


4 


20 


14 


16 


1 


2 


16 


4 


2 





1 








1 






Scarritt 
Quarry 



MULTITUBEECULATA : 

Ptilodontidae 

Insectivora: 

7Deltatheridiidae- - 

Leptictidae.. 

Nyctitheriidae 

Pantolestidae 

Mixodectidae 

Picrodontidae 

Incertae sedis 

Primates: 

Plesiadapidae 

Carpolestidae 

7Anaptomorphidae. 
Inoertae sedis 

Taeniodonta: 

Stylinodontidae 

Oarnivora: 

Arctocyonidae 

Miacidae -. 

Mesonychidae 

Condylarthra: 

Hyopsodontidae. . . 
Phenacodontidae.. . 
Periptychidae 

Pantodonta: 

Pantolambdidae. - . 



' Represented by 1 specimen (less than 0.5 percent). 

The figures represent the composition of the identified collections. 
They are somewhat biased in favor of the multituberciilates, since 
practically all the specimens of these are identified, whereas there 
are numerous isolated teeth of other orders that are not identified, 
but in general they are representative of the faunas as they occur. 

The Gidley and Silberling Quarries agree well, within the probable 
Hmits of chance, except for the much smaller proportion of primates 
and greater of multituberculates in the Silberhng Quarry, a differ- 
ence probably representing slight local facial distinction. 

The surface localities differ remarkably from the quarries and sug- 
gest very different environmental conditions. This result is doubtless 
somewhat biased by the fact that minute forms, like insectivores and 
primates, are more likely to break up and are harder to find at sur- 
face localities, but this does not explain the difference. Some of the 
so-called surface material was, in fact, found in place. These locali- 



62 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

ties have been very closely examined and fragments as small as the 
smallest isolated insectivore or primate teeth recovered, so that the 
almost total absence of those groups must really result from their 
great raritj^ here. Furthermore, the arctocyonids are really much 
more abundant at these localities, for not only the relative but also 
the absolute number of specimens is greater for these localities than 
for the Gidley and Silberling Quarries, despite the much larger col- 
lections from the latter. This "surface" fauna, 90 percent carnivores 
and ungulates, is of more normal type, in comparison with Tertiary 
faunas generall}^, than are the quarry faunas. Its members average 
larger than do those of the quarry faunas, and they are probably 
terrestrial for the most part. This appears to be a normal flood-plain 
facies, rather closely analogous to that of the Torrejon.^^ Its most 
marked peculiarit}'' is the higher percentage of carnivores than of 
herbivores, a condition for which no probable explanation is seen. 

Even at the surface localities there is a surprisingly low percentage of 
animals really of large size for the Paleocene. The phenacodonts are 
of average size for that group, but the periptychids (all Anisonchus) 
are moderate in size, much smaller than the contemporaneous Peripiy- 
chus, and most of the carnivores are also of middle size, wdth Deutero- 
gonodon very rare and other large carnivores absent, although they 
were common at this time in the Torre j on. 

This rarity of large animals is still more obvious in the quarries. 
Phenacodonts and pantolambdids are relatively very rare, Claenodon is 
uncommon, and other large mammals do not occur. The most abun- 
dant species, Ptilodus montanus, IP. sindairi, Leptacodon ladae, Apliro- 
norus fraudator, Paromomys maturus, Palaechthon alticuspis, Meta- 
chriacus punitor, Didymicfis microlestes, and Ellipsodon aguilonius, are 
moderate to minute in size. 

In food habits the multituberculates were rodentlike, the insecti- 
vores doubtless insectivorous (as the word is usually used, not signify- 
ing a diet composed of insects), the primates probably mainly or ex- 
clusively frugivorous, the creodonts in part omnivorous (Claenodon), 
omnivorous-carnivorous (other arctocyonids), and predaceous-carniv- 
orous (miacids), and the condylarths probably browsing, perhaps in 
part frugivorous, or even partly insectivorous for the smallest forms. 
The known fauna apparently consumed every type of food known to 
have been present in the area, with the possible exception of the 
mollusks. 

The skeletal structure is too poorly known for any of these animals 
to give much dii-ect insight into their locomotion or general habitus. 
By analogy and comparison with allied species and genera, the multi- 
tuberculates and insectivores were unguiculate and probably in good 

" Correlation of faunal types and collecting methods is real but indirect. Flood-plain deposition and 
facies would not normally result in concentration of fossils sufficient to permit profitable quarrying. 



FORT UNIOlSr OF CRAZY MOUNTAIN" FIELD, MONT. 63 

part arboreal in habitus. The primates, also, may well have been 
mainly or entirely arboreal. The creodonts were probably mainly 
terrestrial, but it is probable that some of them were at least semi- 
arboreal. The abundant hyopsodontids were probably, judged from 
Torrejon and later allies, more unguiculate than ungulate in general 
habitus, and the smaller forms may well have been arboreal. The less 
common larger condylarths and the very rare pantodonts were prob- 
ably terrestrial. The evidence is not at all conclusive, but it warrants 
the tentative conclusion that this fauna is largely arboreal, which is well 
in accord with the evidence that the quarries were in a swampy and 
heavily forested area and would go far toward explaining the unusual 
facies of the quarry faunas. There is, indeed, a decidedly fossorial 
humerus (of imknown association with teeth) in the collection; the 
facies association of arboreal and fossorial animals is not uncommon 
and is in accord with a forest environment. 

The ordinal composition of the Scarritt Quarry collection differs 
significantly from that of the Gidley Quarry only in the almost com- 
plete absence of carnivores. Within the other orders, the family com- 
position is as nearly similar as would be expected in deposits of similar 
facies but different ages except among the Primates. The abundant 
Gidley Quarry types, Paromomys and its closer allies, are not repre- 
sented in the Scarritt Quarry collection, and instead of them the more 
specialized, perhaps more strictly frugivorous, plesiadapids and car- 
poles tids have become fairly common, although the first were un- 
common and the latter very rare in the Gidley Quarry. 

The Gidley Quarry is also interesting from the unusual occurrence 
of its fossils and the indications of the possible conditions surrounding 
death and burial of its animals. The remains are invariably frag- 
mentary, and with extremely rare exceptions there is no association 
of specimens. The bones seldom show any signs of weathering or 
rolling but are usually fractured, and even when they abut against 
wholly undisturbed matrix these fractures are clean, fresh breaks. 
Some further fracturing and dissociation have resulted from the com- 
pacting of the bed and development of slip planes, but for the most part 
these preceded fossilization. Most of the jaws have lost some teeth 
before burial, and many have lost all the teeth. These isolated teeth 
(clearly lost after death but before burial) are common ia the collection. 
There are many bone fragments, but it is clear that the quantity of 
skeletal material present, even in the most fragmentary state, cannot 
by any means represent all the bones of the animals represented by 
their jaws and teeth. 

The rather abundant presence of fish remains, often in articulation, 
and of aquatic reptile fragments and the presence of aquatic mollusks 
(rare in this quarry, but present), together with the nature of the sedi- 
ments, suggest that the deposit was formed in sluggish water, perhaps a 



64 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

swampy stream course, ox-bow lake, or bayou. From the great va- 
riety of mammals present this evidently was not the site of a single or 
selective catastrophe, like many quarries that seem to represent quick- 
sand or quagmire traps, but must have made a fairly complete sample 
of the mammals of the surroundmg forest and (to a less extent) glades. 
Regardless of whether the mammals came here to drink, swam into the 
water, dropped from trees, or were occasionally washed in, it seems 
likely that the breaking and scattering of their bones, and perhaps 
commonly their deaths also, were the result of activities of the carniv- 
orous fishes and reptiles. Such a history would probably explain the 
small ratio of bones to teeth (the former eaten and digested and com- 
minuted, the latter less palatable and more resistant), the many clean 
breaks, lack of association, and also the common intervention of macer- 
ation, without apparent weathering (perhaps in part digestive, and 
otherwise subaqueous) between death and burial. 

THE GIDLEY QUARRY AND ECOLOGICAL INCOMPATIBILITY 

Matthew (1930) has stated that "we should expect to find in a 
single fossil quarry that the material of each genus represents a single 
ecologic niche, or, if more than one, that they are quite distinct. We 
should not, in other words, expect to find two or more closely related 
species living together at the same time, within the same area, and 
with the same habitat, causing their remains to be preserved together 
in the same quarry . . . Either there would be two or more species 
so widely dift'erent as to belong in obviously independent ecologic 
niches, or else there would be one more or less variable species." 
This is an application to paleontological data of the general principle 
summed up by Cabrera (1932) as the Law of Ecologic Incompati- 
bility in these words: "Las formas animales afines son ecologicamente 
incompatibles, siendo su incompatibiiidad tanto mayor, cuanto mds 
estrecha su afinidad." ^^ 

The Gidley Quarry fauna is ideally adapted to the application, on 
one hand, and to the exemplification and corroboration, on the other, 
of this law and of Matthew's remarks on the taxonomy of quarry 
faunas. The species present in it were certainly contemporaneous, 
and it is highly unlikely that any of the remains can have been brought 
from a point so distant as to have inhabited distinctly different areas. 
The general envu-onment was probably essentially the same for all, 
although unquestionably it included distinct ecologic niches. It is 
possible that deposition extended over a period of years and that there 
was some seasonal or other periodic change in the species of the 

" I do net wish to claim for Cabrera a degree of originality that he disclaims for himself. Cabrera's law 
has been recognized in various forms by many authors and for a long time, but as far as I know it has never 
been more exactly explained and exemplified or placed more clearly on its true ecologic (not geographic) 
basis than by Cabrera. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 65 

neighborhood, but this is purely hypothetical. It is most reasonable 
to conclude that all these animals did live together, at the same time, 
witliin the same area. 

It is therefore to be expected that genera present in this quarry 
will either have only one species each or will have species not inter- 
grading at all and reflecting structurally their pertinence to different 
ecologic stations in the area. With this in mind, the assumption was 
made in dealing with each genus that it did include (in this quarry 
fauna) just one species unless the contrary could be proved beyond 
reasonable doubt. 

Matthew, in the paper cited above, and most other writers on the 
question of species making in paleontology have insisted on making 
due allowance for variation, or using for taxonomy only non variable 
characters, but they have adduced no real, objective criterion as to 
what "due allowance" should be, and they sometimes seem to over- 
look the fact that there is no such thing as a truly and completely 
"nonvariable" character. Not merely as mechanical, mathematical 
procedures but as a general system of logic and a grouping m^ethod 
useful both explicitly and as an implicit background for dealing with 
both numerical characters and attributes, the methods of statistics 
provide the desired means of measuring variation accurately and the 
necessary criterion as to whether this variation is or is not of the sort 
normal Avithin a species. These tests and this logical background 
have been the basis for taxonomy in tliis study. If the specimens 
pertaining to one genus could not indubitably be separated into differ- 
ent groups, the conclusion has been that the fundamental hypothesis 
of one species to each genus was correct. If they necessarily had to 
be separated into different groups, and these groups could not be 
interpreted as based on nontaxonomic differences (such as age or 
sex), then and only then has the liA'^pothesis been discarded. 

Since tliis largely objective testing has intervened, it is not arguing 
in a circle to start the study with the assumption that Cabrera's 
Law applies, and then to consider the results as a test of the validity 
and an example of the operation of that law. (See figs. 3 and 4.) 

The actual results are as follows: Tliirty genera are represented in 
the Gidley Quarry by one species each. Since this includes the greater 
part of the quarry fauna, in general it is true here that the related 
(congeneric) animals living at that time in this area were of the same 
species. The apparent exceptions belong to six genera, each of which 
is worthy of brief special consideration. 

The multituberculates, with four species tentatively referred to 
Ptilodus and three to Edypodus, are the most striking apparent 
exceptions. In the fu'st place, however, the generic designations are 
very dubious. It is not at all certain that the species referred to 



66 



BULLETIN 169, UNITED STATES NATIONAL MUSEUM 











EUjpsodor? 








10-1 


Lifomylus 
cfissenfaneus 

1 r— ^ 


rui/onius 




5- 




Litalefes 
disjuncfus 




Haplaletes 
oliscepfafrix 


• 




— 






Z 




I 1 


^- 


— V 


. , ... 


1 1 





2-35 2.75 315 355 3-95 4-35 

LENGTH Ml, HyOPSODONTIDAE 



10 



5- 



P depressidens 



P.moturus 



2.05 lAb 2.S5 3.25 
LENGTH Mz,PAROM0MYS 

Figure 3.— Histograms illustrative of Cabrera's law as applied to the Gidley Quarry fauna: a. Length 
of Ml in hyopsodcntids: in this and some other measurements the species nearly or quite intergrade, 
and they lived in the same place at the same time, but they are morphologically very distinct and belong 
to four different genera; b, length of M2 in Paromomys: the two species are morphologically similar, 
probably are congeneric, and are found together, but in this dimension and in many other characters 
they do not intergrade. 



M. provocafor 




A.O 4.3 4.6 4.9 5.2 5.5 5.8 6.1 

Length Ma 



M.p 

1 

6 
5 


uniioi 

m 


M. 


provo 


catoi' 


3 


B 




^S 



Quarry Specimens. 

Of her Upper Lebo Specimens. 

One specimen in each sample. 



4.0 4.3 A.Q 4.9 5.2 
WIDTH M2. 



Figure 4. — Histogram of measurements of second lower molars of all Lebo specimens of Metachriacus. 
The distributions of these measurements, which are distributed much as are most of the characters of 
the samples, are clearly bimodal, and two entities are shown to be present. These entities intergrade, 
but they are separated by provenience, the two coming from different horizons and localities within the 
Lebo. They are thus interpreted as closely allied but separable species. If they occurred together, a 
more probable interpretation would bo that they represent the two sexes of a single species. 



FORT U:MIO]Sr of crazy mountain field, MONT. 



67 



Ptilodus or to Ectypodus are really congeneric in each case. There 
may well be one or more other genera represented here, although it 
does seem unlikely that each species could belong to a different genus. 
Aside from this possibility, the species referred to one genus are in 
every case sharply distinct from each other, with no intergradation 
shown. This is true of many different characters, and is well shown 
by table 5 of observed ranges of a few numerical characters: 

Table 5. — Ranges of numerical characters in multituberculates, Gidley Quarry, 
Crazy Mountain Field, Mont. 



Genus and species 



Ptilodus: 

montanus 

douglassi. 

gidkyi 

sinctairi.. 
Ectypodus: 

grangeri.. 

russelli... 

silbcrlingi 



LP4 



Mm 
7. 1-9. 1 
6. 5-6. 8 
6. 9-6. 1 
2. 5-3. 7 

5. 2-5. 4 

4. 9-5. 1 

3.3 



LM, 



Mm 

3. 2-3. 7 
3.7 
2.5 

1. 7-2. 

3. 3-3. 4 
2.9 
2.3 



LP4:LM, 



2. 3-2. 4 
1.8 
2.4 

1. 3-2. 

1. 5-1. 6 
1.7 
1.4 



Serrations 

P4 



13-15 

13 

14-15 

10-13 

13-14 

13-15 

12 



Cusps Ml 



5-6:4-5 
6:4 



6-7:4 



10-11 
9-10 



6-7 

6 

5-6 



Thus these species probably represent more than two genera and in 
any case are so sharply distinct that each must have had its own 
ecologic niche. They do not intergrade, but in some cases, notably 
P. montanus, there are known species, in this case P. mediaevus, 
with which they do nearly or quite intergrade but which did not live 
together with them. In short, these are not exceptions to but are 
strildng exemplifications of Cabrera's law. 

Leptacodon is here credited with two species. Their tooth dimen- 
sions do not intergrade, although the degree of variation is well 
established for one of them, and there are structural differences such 
that they may well prove to be distinct subgenerically, or even 
generically, when both are more completely known. This is even 
more strikingly true of the two species referred to Paromomys, which 
are so different that I was for a time inclined to separate them 
generically (see fig. 3, b). Didymidis also is represented by two 
species perhaps not really congeneric, not intergrading at all and one 
reaching a size nearly twice that of the other. 

In the case of Claenodon, Gidley has been followed in listing three 
species from the Gidley Quarry, all of about the same size and general 
character. Differences between them do exist, but the material is 
inadequate to establish the extent of variation, and when this is 
established I suspect that the supposed three species will prove to be 
variants of a single species. If not, this will be the unique example 
of the occurrence of two or more closely related and apparently 
ecologically similar species in the quarry. 



68 BULIjETIN 169, UNITED STATES NATIONAL MUSEUM 

EXTENT OF KNOWLEDGE OF MIDDLE AND UPPER PALEOCENE FAUNAS 

Aside from details concerning only special students, the impor- 
tance of such collections as those here described lies, from a more 
general point of view, in the knowledge they give of the broader out- 
lines of mammalian life in their time and area. To permit the proper 
drawing of inferences in this broader field, it is essential to consider 
the adequacy of the collections and their probable relationship to the 
faunas as a wdiole represented by them. The adequacy of a paleon- 
tological sample depends principally on three quite distinct factors: 

1. The adequacy of the collection studied as a sample of the fos- 
sils actually preserved in the rocks. 

2. The adequacy of the preserved fossils (collected or uncollected) 
as a sample of the whole fauna that actually lived in the area. 

3. The adequacy of the real local fauna as a sample of the regional 
fauna of the whole land mass on which it lived. 

Probably the best criterion of the adequacy of a collection as a 
sample of the preserved fossils is that of repetition. "When collecting 
begins to pile up mainly or only duplicates, it probably has achieved 
sampling adequacy for the local deposit, but as long as many species 
remain very rare in collections, it probably has not. 

Of the 51 surely separate species known from the Gidley and 
Silberling Quarries, 15 are here represented by only one specimen each, 
but of these four are known by other specimens from elsewhere in the 
field. Seven here have only two specimens each, but one is fairly 
common elsewhere. Six are here known from three specmiens each, 
but two are also represented elsewhere. The other 23 species are 
represented by five or more specimens each from these quarries. In 
the field as a whole, of the 79 species, 19 are represented only by one 
specimen. Four of these represent genera still unknown elsewhere, 
and hence loiown from but one specimen each: Stilpnodon simplicidens, 
Unuchinia asaphes, Elphidotarsius Jlorencae, and Spanoxyodon 
latrunculus. Of the other 15 species here represented by only one 
specimen each, three (Leptacodon cf. tener, Psittacotherium multi- 
fragum, and Thryptacodon laustralis) are inseparable from species 
well known in other fields, and the others all belong to genera well 
known from other species, some of them abundant. For broader 
studies of morphology and faunal succession, local species are not 
very important, and of the 51 genera known to occur in this field, 
not more than five can be considered as very poorly represented in 
Middle Pal eocene faunas generally.^* 

From these data, as well as the general make-up of the collections 
and other considerations, the collections appear to represent the real 

i» At least one of these, Elphidotarsius, and possibly one or two others are closely allied to well-known 
genera. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 69 

fauna ^° of the region fairly well but far from completely. The high 
proportion of species loiown here from only one specimen each, about 
25 percent, shows that the collections, large as they are, are not yet 
adequate to give a proper sample of the species that may be pre- 
sumed actually to be available here as fossils. Such a high percent- 
age of very rare forms indicates clearly that any further collecting 
is almost certain to add to the number of known species. 

As far as mference can be drawn from these data and from ecologic 
and similar considerations, the situation regarding the v>'hole pre- 
served (but only partly collected) sample, that is, the forms that were 
actually fossilized, is much better, but not perfectly satisfactory. It 
may reasonably be assumed that there was in tliis general region 
some variety among the larger and possibly plains-dw^elling types, 
such as are common in the Torrejon and also in the later Paleocene 
and early Eocene in acljacent areas, but their great rarity or absence 
here and the general facies present strongly suggest that the condi- 
tions of deposition were such that some and perhaps many of these 
were not preserved and so will never be known in tliis area, no matter 
how large the collections made. 

On the other hand, knowledge of the general composition of the 
Middle and Upper Paleocene mammalian faunas of North America 
as a whole may now be considered very good. It is probable that 
we have representatives of almost all the orders and families and a 
large majority of the genera,'^ that occurred on this continent during 
that time. The combined area represented by collections is now very- 
considerable, on the order of 1,000 square miles of actual collecting 
territory, representing many times that in the ranges of sampled 
faunas. The environmental variety represented is apparently great, 
for the sediments yielding mammals of these ages are of many dif- 
ferent sorts, many genera are represented by several well-defined 
species in each, and the inferred habits of the various known mam- 
mals include almost every possible terrestrial mammalian habitus. 
The collecting areas certainly were part of a unified North American 
land mass in the Paleocene, extend more than 1,200 miles north and 
south, and w^ere probably central on that land mass, ideally situated 
for a representative sample of the whole North American fauna. 

20 It would be rather hopeless to crusade against the UBiversal and careless habit of calling a collection a 
fauna. By "real fauna" is meant what should properly be called simply"fauna"; that is, the totality of 
mammals that actually lived in this area, and not merely those that happen to be known or the collection, 
a sample, on which this knowledge is based. 

2' In accordance with the tentative views as to adequacy of local samples expressed elsewhere (Simpson, 
1936a). 



PART 2: CLASSIFICATION AND DESCRIPTION 
OF MAMMALS 

Order MULTITUBERCULATA Cope, 1884 

Douglass' first collection included no multituberculates, but in his 
second collection (see Douglass, 1908) there were several teeth of this 
group. A jaw fragment with P4 and Mi was made type of Ptilodus 
montanus, and other specimens of that species were mentioned. 
Several upper teeth were referred to Chirox, not then known to be 
S3^nonymous with Ptilodus, and the probable presence of other species 
of Ptilodus was mentioned. An incisor with limited enamel band 
(Douglass, 1908, pi. 1, figs. 18, 20) was tentatively referred to Mixo- 
dedes but may also be multituberculate (cf. Eucosmodon) . 

Among the first discoveries made by Mr. Silberling for the Na- 
tional Museum was the now famous specimen that includes skull, 
jaws, and some skeletal parts of Ptilodus. This was described, as a 
new species, Ptilodus gracilis, by Gidley (1909) in the first of his 
notes on this fauna. This is still the finest single multituberculate 
specimen known. It enabled Dr. Gidley to demonstate that Chirox 
is merely the upper dentition of Ptilodus (and by analogy, Bolodon 
that of Plagiaulax, in the Jurassic) and for the first time to establish 
the true characters of this extraordinary group. He concluded that 
Ptilodus and its kin were diprotodont marsupials. Although this 
conclusion now seems untenable, it should be emphasized that such 
a conclusion was logical, if not inevitable, at the time ^^ and that 
Gidley's work on this form was very able. Gidley also noted the 
presence of at least two other, smaller, species in the Fort Union 
collection, although the limited material then available did not per- 
mit their description, and he tentatively referred them to two Cre- 
taceous species described by Marsh. 

Granger and Simpson (1929), revising the Paleocene multitubercu- 
lates, restudied Ptilodus montanus, Douglass' type, concluding that 
it was doubtfully distinct from Ptilodus mediaevus and P. gracilis. 
The latter species was not reexamined, as Dr. Gidley was then living 
and planning a definitive study of liis material. It was suggested 
that no valid distinction from P. montanus had been given, but the 
species was accepted pending Dr. Gidley's definitive study. Two 
Torrejon specimens were doubtfully (and, as now appears, incorrectly) 
referred to P. montanus. 

As regards these three species, the conclusion below is that Ptilodus 
gracilis is a synonym of P. montanus, which is distinct from the 
Torrejon P. mediaevus, although very closely related. 

22 Interesting unpublished correspondence shows, for instance, that Dr. W. D. Matthew went over 
Gidley's argument with great care at the time and agreed with his conclusion, although later new evidence 
forced him to change his mind and to reach essentially the conclusion here supported. 

70 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 71 

Dr. Gidley had evidently formed definite conclusions as to the 
classification of the whole group in the Fort Union collection, for most 
of the labels bear specific names, several of them new. Two or three 
of the new species described below correspond approximately with 
some of those recognized by Gidley, but as the correspondence is not 
exact even in these cases and as my classification is otherwise much 
unlike that suggested by Gidley's labels, it is evident that he did not 
emplo}^ the criteria here used. As he left no notes or manuscript 
relating to this group, I am forced to treat it de novo (except, of 
course, for his preliminary publication). 

As shown by the figures given elsewhere, multituberculates made 
up a large proportion of the collection and are the most important 
single element in the fauna. 

AFFINITIES OF THE MULTITUBERCULATA 

This material has had such a decisive influence in the consideration 
of the affinities of the Multituberculata that the subject must be 
mentioned briefly here, although it has been thoroughly reviewed 
elsewhere (Simpson, 1929c, 1929e; Simpson and Elftman, 1928; 
Granger and Simpson, 1929). 

The earliest ideas (Falconer; Owen; Marsh; Cope, 1884; Osborn, 
1888), influenced by the descriptive analogy of the shearing teeth to 
those of some diprotodont marsupials (and a few other inconclusive 
characters), were that the multituberculates were marsupials. When 
the teeth of Ornithorhynchus were discovered, Cope saw in them 
some resemblance to the multituberculates and suggested that the 
latter were monotremes.^^ 

When the fine specimen of Ptilodus here redescribed was discovered, 
it gave Dr. Gidley the first real opportunity to study the problem on 
a broader basis than that aftorded by the often misleading dental 
characters. After a careful, but only provisional, analysis, he con- 
cluded that Ptilodus and the other multituberculates are diprotodont 
marsupials, diverging from those of Australia in the Jurassic or even 
in the earlier Triassic.^* 

Broom (1910) restudied Tritylodon and critically examined Gidley's 
publication, concluding that the multituberculates were an indepen- 
dent group without near affinities with the living monotremes, mar- 
supials, or placenta,ls. Later (1914) Broom studied Gidley's original 
and also a skull of Taeniolabis and then concluded that the multi- 
tuberculates were monotremes. 



23 A few theories unworthy of further serious consideration are passed over without any notice. All 
have been listed and refuted in previous papers. 

2< This and several other points in his Fort Union work demonstrate Gidley's belief in the extreme antiquity 
of modern groups of mammals and their polyphyletic evolution. This philosophical consideration underlay 
much of his work and colored many of his conclusions. Specifically, he believed the Australian mammals 
to have been differentiated in the Mesozoic and outside of Australia. See also Myrmecoboides, below. 

119212—37 6 



72 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

Matthew (first in 1915) and Granger (1915 and subsequently), 
however, reviewed all the evidence of Gidley and Broom and also 
some very important new evidence (chiefly hind limb of Eucosmodon) 
and reached a conclusion similar to Broom's first opinion, that the 
multituberculates are not closely related to any other known mammals. 
I reached this same opinion independently, and I have reviewed all 
the evidence and added to it in several studies. 

The new evidence from the Fort Union specimens, which I had 
seen but not studied (except through Gidley's publication) before 
writing my previous papers on multituberculates, is not very exten- 
sive. I confirm Broom's opinions that the jugal is probably small in 
Ptilodus and not entering the glenoid, that there is no evidence for 
an ahsphenoid bulla, and that there may be an uncoiled cochlea 
(although I consider this unproved), as well as the point already 
checked on other material that there is no true angular process. On 
the other hand Broom's evidence regarding the shoulder girdle was 
certainly incorrect,^^ and I have elsewhere indicated that the teeth 
do not support monotreme relationships.^^ The few new details 
regarding skull structure, foramina, etc., that I have been able 
to make out show a rather generalized structure with no special 
characters either of monotremes or marsupials. The humerus, the 
only known skeletal element not fully considered in my previous analy- 
sis, seems to me to be neither distinctly therian throughout, at least 
in a taxonomic sense, as Gidley believed, ^^ nor in its articular portion 
nearer to the monotreme than to any higher type, as Broom believed. 
Of the two, it seems to me superficially and adaptively much nearer 
the Theria, but fundamentally distinct from both. 

In conclusion, the present study confirms and to a slight degree 
strengthens my former opinion, anticipated by Matthew and Granger 
and still earlier by Broom but abandoned by the latter, that the mul- 
tituberculates are a distinctive group not ancestral or closely related 
to any later mammals and of extremely ancient separation from the 
main mammalian stock. The very real resemblances to the Theria, 
pointed out by Gidley, seem to be superficial and adaptive and to 
indicate analogous stages of evolution, not blood relationship. The 
likewise real resemblances to the monotremes, pointed out by Broom, 
seem to be in part adaptive, in part due to the retention in two fairly 
conservative but not especially related lines of a few very primitive 
characters, inherited from the mammal-like reptiles. 

25 His conclusion might (but improbably) prove correct, but the evidence is not. The shoulder girdle is 
known only from one fragment (Djadochiatherium) , not conclusive but rather opposed to Broom's view. 

28 This was the basis of Cope's behef in such relationships, and Broom added it to his table of evidence 
but placed no great weight on it. 

" Gidley says "eutherian", which was made the subject of a correction by Broom. In fact, Gidley was 
right, historically, in his use of the term, since Eutheria was originally defined to include both marsupials 
and placentals, and he was using it in that sense. It is surely less misleading at present, however, to follow 
the more current usage of Metatheria for the marsupials, Eutheria for the placentals only, and Theria for 
both together. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 73 

METHODS OF STUDY 

The identification of this large multituberculate collection and its 
classification in genera and species have been peculiarly difficult, and 
the work was accomplished, as far as it was possible at all, only after 
prolonged and tedious analysis. Much of it led to no useful result and 
so is wholly omitted here. An outline of the useful methods employed 
■will, however, be given, because they are similar to those used through- 
out this v/ork and are in some parts unfamiliar to many paleontologists. 

In the first place, it was found that although at least three, and 
probably four or five, genera are represented, it was not practical to 
begin v^^ith a generic grouping of the specimens, as is the more usual 
practice. The greater part of the collection consists of lower jaws. 
With very few exceptions, which proved to be of little practical 
assistance, the upper jaws all belong to a single species, and in only 
one case are upper and lower jaws associated. In the family Ptilo- 
dontidae the genera are usually readily distinguishable on the basis 
of upper teeth, but in several cases, notably Ptilodus and Edypodus, 
they are practically indistinguishable from lower teeth alone. The 
only really clear-cut generic distinctions in the lower dentition so far 
recognized depend on the nature of the incisor, whether compressed 
and with limited enamel band or not, and in the presence or absence 
of Ps.^^ In the present collection, only a few fragmentary specimens 
(without cheek teeth) have an Eucosmodon-like incisor, and only one 
P4 lacks the notch for P3. These characters are therefore not available 
for the bulk of the collection, and it was necessary to treat the whole 
collection as if it represented only one genus, to distinguish the species 
present, and then to attempt to place them in genera. 

The following observations were made and recorded for each 
specimen in the collection: 

IsTumerical: 

Dimensions: 

Length of P4. 

Length and width of Mi, M2, P', P^, P^, P^^M^ and M^. 
Ratios: 

Length P4 : Length M,. 

Length Mi : Width Mi. 

Length Mi : Length M2. 

Width Ml : Width M2. 

Length Mj : Width M2. 
Counts: 

Serrations of P4. 

Cusps of Ml, M2, P3, F\ Ml, and'M2. 
Nonnumerical: 

Presence or absence of P3. 

Character of incisor. 

Shape of P4. 



>9 The peculiarly reduced P4 of Mkrocosmodon Jepsen is also a good generic distinction, but this strange 
orm does not occur in the present collection. 



74 



BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



The dimensions and ratios are, from a statistical point of view, 
continuous variates. The counts are discontinuous variates. The 
nonniunerical observations are attributes and to these is to be added, 
for comparison with other collections, the provenience of the speci- 



mens. 



■S3 



? Ecfypodus 



? Ecfypodus 3. 
russelli 2 



''.Pfihdus 




sinclairi . 




1 1 


? Ecfypodus 


' 


^ilberlingi 




\ 1 



7 a 9 10 n 5 6 7 8 9 10 11 

NUMBER OF EXTERNAL CUSPS Ml 

POSITIONS OF TYPE SPECIMENS 



"f Pa fee iy pod us J epseni 

^Ecfypodus Silberlinai 



Ptilodus graciJiS' monfanus 
„ Ptilodus monfanus 

? Ecfypodus russelU 

„^ , ? Ptilodus 

?Ectypodu3 jyou9/ass: 
grangen ^ 




2.0 



3.0 

Ptilodus sindain 



Y^Ectypodus 

■— ' ^'^ snbeding. 



A.O 



5.0 



6.0 7.0 

\? Ptilodus gidleyi 



8-0 9.0 

Ptilodus monfanus 



Tatecfypodus^ 

jepseni _ 

?£cfypodus ,^]}? Ecfypodus gran^en^'^Plilodus douqlassi 



russelli 
FORT UiNIOM PTILODONTID/C. 



LENGTH P4. 



Figure 5.— Histograms of typical variates of multituberculates from the Qidley and Silberling Quarries: a. 
Number of external cusps on Mi in four species; 6, length of Pi in the whole sample, with division of 
species based on the study of this and all other available characters. 



The same data were recorded for the much fewer Torre j on speci- 
mens (American Museum collection) and, from publications, for the 
types of other known species available for comparison. 

The numerical data were then all plotted graphically in several 
different ways, a few of which are here reproduced (figs. 5-7). Tenta- 
tive grouping was then attempted, by taking each graphic representa- 
tion and dividing it into as iew groups as possible. For instance, the 
length of P4 histogram was at first divided into only three groups, 
one from 2.45 to 3.95 mm, one from 4.85 to 5.45, and one from 5.75 
to 8.75. (The single specimens at 4.3 and at 9.1 were left doubtful 
and later disposed of as shown, on other data.) 

It was then found that the groupings on different characters did 
not include the same specimens. For instance, in the grouping on 
length of P4 the type of silberlingi (see below) is quite indistinguishable 

2» Almost all are from the Silberling or Gidley Quarries, and the few that are not from these do not differ 
significantly. Provenience was therefore not a useful datum in sorting out the collection, but only in com- 
paring it with other collections. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



75 



from the sinclairi group, but in the grouping on external cusps of Mi 
it is clearly distinct. Or, as another example, the gidleyi and douglassi 
groups are not well distinguished in either of these diagrams, but are 
far apart in the scatter diagram of length Mi and length P4 (as they 
are also in others not reproduced). By continuing this process, eight 
groups were eventually distinguished. A smaller number than eight 
was inconsistent with the distribution of two or more characters, 
and a larger number not necessary to interpret the distributions. 




Figure fi.— Histogram and corresponding roughly fitted normal curve of length of P4 in Ptilodus montanus 
from the Qidley and Silberling Quarries. The distribution is the same as that for this species included 
in flg. 5, 6. 



59 

H 
I 

b 







DOUGLASSir 


GRANGERI; 


•"•) 


RUSSELLlQ 


,-^ 




JEPSENI 


• • 




SiLBERLINGI 




GlDLEYI'.'-'' 









, '''MONTANUS 



'2.0 



5.0 50 

LENQXH 



8.0 



9.0 



P4 



Figure 7.— Scatter diagram of length of M: and length of Pi for all Gidley and Silberling Quarry specimens 
of multituberculates that show both of these measurements, with separation into species based on this 
and all other characters. 

The two most abundant groups {sinclairi and montanus in the classi- 
fication as finally worked out) were then tested for homogeneity, by 
statistical methods which showed that their deviations from normal 
form in any case are not of probable significance, and then for numer- 
ous continuous variates of each of these groups the mean, standard 
deviation, coefficient of variation, and the standard errors ^° of each 



"> I have given standard errors throughout. 
0.6745 times this figure. 



The probable error, which has nothing to recommend it, is 



76 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

of these were calculated. These new figures furnished a check on the 
probable taxonomic significance of the grouping. A priori, the range 
of variation allowed by the graphic grouping appeared too large for 
single species. Most paleontologists would think it wholly unjustified, 
for instance, to place a lower premolar measuring 7.0 mm in length in 
the same species with one measuring 9.1. But the coefficient of 
variation of the whole group to which these belong is only 5.3, and that 
is small, rather than large, for a Imear dimension of teeth of a single 
mammalian species, so that there is no reason to believe that the graphs 
have permitted confusion of two species. 

These statistical data, furthermore, when considered from a taxo- 
nomic biological viewpoint, suggested the degree of variation to be 
expected in species of tliis family and also gave a criterion for judging 
the greater or less usefulness of certain characters for taxonomic dis- 
tinction. Thus, in turn, a check was possible on the groups too small 
for the useful calculation of these derived data. 

After full consideration of all these primary and secondary data, 
it was clear that of the eight groups finally achieved and checked each 
represents a variable morphological unit, that the variation in each is 
not greater than commonly occurs in natural species, but that no two 
can be combined without producing a unit statistically heterogeneous 
and morphologically much more variable than a species. The biologi- 
cal conclusion is thus that eight species are present. 

Eight species of a single family seems a relatively large number to 
occur at a single horizon and locality ,^^ but there is really nothing 
extraordinary in this number. The ptilodontids are analogous to small 
rodents, and there is, for instance, hardly any region of the United 
States today that does not have more than eight species of Cricetidae. 
This large number of species clearly is not due to maldng the specific 
distinctions too small. On the contrary, since we have definite, con- 
crete statistical data warranting this, allowance has been made for 
much more variation than is usually granted within a paleontological 
species. The largest individual of sindairi, for instance, is 48 percent 
larger than the smallest (length of P4), a much greater variation than 
the current rule-of-thumb methods permit, although the demon- 
strable probability that they do belong to one species is very great. 

A few specimens could not be placed in any of these eight species. 
A Eucosmodon-\ike lower incisor, for instance, probably does not belong 
with any of them. (It is also from a difterent locality.) Several 
upper teeth, not of montanus, cannot be associated v/ith lower jaws, 
and wliile they almost certainly belong among the species based on 

31 All these species occur in the Gidley Quarry. While the specimens from the Gidley Quarry cannot all 
be exactly contemporaneous, they are practically so. Nevertheless the probability that they represent a 
succession of years or seasons helps to explain the faunal variety, not by the evolution of new species but by 
the opportunity for more thorough sampling of a large area. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



77 



lower teeth they must be left incertae sedis wdth respect to them. It 
was, however, possible to place all the lower jaws with P4, Mi, or both 
in one of these species. 

It was next necessary to compare these eight species with those 
previously named and described. Ptilodus mediaevus and troves- 
sartianus, the onl^^ named approximately contemporary species, 
demanded closest comparison. The probably later species Edypodus 
musculus, E. cochranensis, Paredypodus simpsoni, and P. tardus were 
also compared. No others are sufficiently close to warrant detailed 
comparison. 

At this point the attribute of provenience becomes of essential 
importance. As an example, the number of serrations on P4 of the 
montanus group from the Fort Union, counted on 29 individuals, 
varies from 13 to 15, the mean being 13.8 and the median 14. In the 
six available individuals of comparable size (mediaevus group) from 
the Torrejon, five have 12 and one has 13 serrations, mean 12.2, 
median 12. If all these be considered as one sample the distribution 
is: 

12 serrations — 5. 14 serrations — 19. 

13 serrations — 9. 15 serrations — 2. 

The distribution shows no bimodaiity, and it might be assumed that 
the sample is homogeneous with respect to this character, but this is 
fallacious, as the sample is not, in fact, drawn from one population. 
Table 6 shows the distribution of 35 individuals with serration count 
of P4 and provenience considered as attributes. 

Table 6. — Contingency tabic of serration counts and provenience for 35 specimens of 
Pi of the Ptilodus mediaevus-montanus group 



^^^^ Serrations 
Locality' ^\^ 


12 


13 


14 


15 


Montana 





8 


19 


2 


New Mexico 


5 


1 









Although the data are inadequate for the calculation of coefficients, 
it is clear that there is positive association of Montana and 14 serra- 
tions and of New Mexico and 12 serrations, and this association is of 
significantly greater degree than would be expected from effects of 
random sampling. In spite of the fact that the two samples overlap 
in this respect and that they could not be separated if they were from 
one population, it is clearly very probable that the two populations 



78 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

from which they were, in fact, drawn do differ in the mean number 
of serrations. 

Similar differences associated with provenience occur in several 
other characters and show that Piilodus mediaevus and P. montanus 
are distinct. They could not be certainly separated if they occurred 
together, although even in that case the significantly greater varia- 
tion of the combined samples would lead one to suspect that the 
population was heterogeneous. 

If we accept the specific groupings finally adopted as valid, some 
interesting conclusions regarding variability and the value and signifi- 
cance of various characters for taxonomy in these animals are possible. 

The length of P4, the most useful single dimension as this is far the 
commonest tooth in multituberculate collections, has a coefficient of 
variation of 9.3 ±1.6 in the sinclairi group. This is high, but com- 
parably liigh coefficients have been recorded for linear dimensions of 
teeth of mammalian species. ^^ In the montanus group this coefficient 
is 5.3 ±0.6. This dimension is thus much less variable in the avail- 
able sample of the latter species and to that extent seems a more 
reliable taxonomic character for it than for the smaller sinclairi. ^^ 
On the other hand, the length of Mi in the sample of sinclairi is very 
constant, coefficient of variation only 4.4 ± 1.1, and in montanus some- 
what more variable, coefficient 5.7 ±1.35. 

Thus appear the interesting facts that in sinclairi P4 is highly 
variable and Mi little variable in length, v/hile in montanus both are 
moderately, and about equally, variable. As a result of these facts, 
the ratio length P4 : length Mi is very much more variable in sinclairi 
(standard deviation 0.22 ±0.06) than in montanus (0.04 ±0.01). This 
is also accentuated by the further fact that in montanus, but not in 
sinclairi, these two dimensions are positively correlated, that is, that 
in montanus the larger premolars tend to be associated with the larger 
molars, while in sinclairi the available data show no such tendency. 
Another expansion of this same unexpected and important fact, clearly 
visible on the scatter diagram (fig. 7), is that in sinclairi the line of 
regression of length Mi on length P4 is horizontal or even slightly 
inclined downward to the right, coefficient nearly zero or a very small 

32 E. g., in Pal. Sin., ser. C, vol. 5, fasc. 5, Helga Pearson gives coeflBcients up to 11.4 for M^ of one side 
in one sex of a single homogeneous human race and coefficients up to 8.1 for probably very homogeneous 
groups of fossil suids. 

33 How misleading the best judgment may be when not aided by statistical treatment is shown by the 
fact that although Gidley clearly relied on size of P4 chieily for specific separation (as shown by the nature 
of his groupings and also by his unpublished specific names, all of which denote size), he placed the small 
sinclairi specimens in one species but divided the large montanus into three species, although the variability 
of the former Is nearly twice that of the latter. The misleading factor is that the absolute difference in the 
extremes is less for the small than for the large species. Although this is the striking character to the eye, 
it is not the essential factor either from a statistical or from a biological point of view. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 79 

negative fraction, while in montanus it is inclined upward to the right, 
coefficient a significant, positive, fraction.^^ It is quite possible 
although unprovable from these data that the distinctly different 
type of variation in these two species characterizes difterent generic 
groups. 

The ratio length Mi to width Mi has a standard deviation of 0.17 ± 
0.04 in sinclairi and 0.13 ±0.03 in montanus. The means of the two, 
2.2 and 2.0, respectively, do not differ enough to prove that they are 
a reliable method of distinguishing these species. The character may 
however, be taken as of taxonomic value in such cases as that of 
silberlingi where this value, 2.6 in the unique specimen, deviates 
significantly from the mean for sinclairi (deviation more than t"wdce 
the standard deviation of the latter). There is a group of species 
that seems to be characterized by a high value for tliis ratio, or 
descriptively by a relatively long and narrow Mi, including silberlingi, 
russelli, and grangeri in tliis fauna and Ectypodus musculus and 
Paredypodus tardus in other Paleocene American faunas. 

There are too few specimens with M2 to provide adequate data, but 
with its variability assumed to be about that of Mi, its length: width 
ratio would appear to be a valuable character distinguishing Piilodus 
mediaevus and montanus, in both of which the ratio averages 1.4 in 
the known material, from ail other species in which it is known 
averaging 1.7 to 1.9. 

The length of P^ in the montanus group has the very high coefficient 
of variation 18.5 ±2.86. This is, generally, too high a coefficient for a 
sample of one species, yet the other coefficients for the upper teeth 
are of more reasonable size, 10.0 in the case of length M^ and con- 
siderably smaller for the other dimensions used. It is possible that 
some extraneous P^'s have been included, but more probable that they 
are all of one species and that this tooth, in any event visibly reduced 
and in process of becoming vestigial, is extreme^ variable in length. 
In either case, its length is not a reliable specific character. The 
number of cusps on this tooth, varying from fom' to seven in all the 
specimens of tliis family in which it is known, seems at first sight to 
be a helpful character and has been used in specific diagnosis, but 
probably it is not. In specimens that, on all other data, rather 
clearly represent one species, montanus, this cusp number shows the 
full range of variation for the isbvnily, 4 to 7. The data, as well as 
those for P. mediaevus, are given in table 7. 

s* The samples are inadequate for the useful exact calculation of the regression equations, but their general 
nature is visible. 



80 



BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



Table 7. — Distribution of 23 specimens of Ptilodus montanus and P. mediaevus 
on the basis of the number of cusps of P^ 



"^\ Cusps Ps 
Locality "^^^ 


4 


5 


6 


7 


Montana (montanus) 


13K 


5 


' lOK 


1 


New Mexico {mediaevus) . 


2 


1 









« Where it is doubtful whettier a cuspule should be counted or not, I have counted the specimen as one- 
half for each of the groups to which it might belong. 

The median for montanus is 6 and for mediaevus 4, and this may be 
a specific character, but the distributions fully overlap and the 
samples do not suffice for adequate determination of the significance 
of this dift'erence. Until larger samples are at hand, this character 
cannot be used with certainty to distinguish species. 

Passing other characters in more rapid review, the number of cusps 
of Ml, particularly in the outer row, shows a range of not more than 2 
in each species, even in the largest samples (which are, however, 
small, not exceeding 9) and differ markedly from one species to another, 
probably afi^ording good specific or even generic characters when the 
means differ by tw^o or more. The external cusps of P^ are highly 
variable (range 0-3 in montanus) and the data inadequate for proper 
evaluation, but probably a marked deviation in the medians has 
specific significance. The inner row varies less in this material (9-10 
cusps) and probably has specific value (8 in mediaevus), and the width 
of this tooth is a valuable although variable character, coefficient of 
variation 8.4±1.7 in montanus. The one available specimen of 
mediaevus shows a deviation from the means of montanus nearly three 
times the standard deviation of the latter, almost certainly significant. 
Other teeth are known in so few cases that their characters cannot be 
evaluated. 

Family PTILODONTIDAE Simpson, 1927 

Six valid genera of Ptilodontidae have so far been described from 
the American Paleocene. Their characters are summed up in the 
following artificial keys: 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



81 



KEY TO AMERICAN GENERA OF TERTIARY PTILODONTIDAE (LOWER JAWS) 

7. Lower incisor little or not compressed, relatively smaller, more 
completely enameled: 

A. Anterior base of P4 notched: 

1. P4 longer than Mj, numerous serrations and strong ridges: 

a. Ml relatively longer, more cusps Ectypodus ^' 

b. Ml relatively shorter, fewer cusps Ptilodus ^' 

B. Anterior base of P4 not notched: 

1. P4 longer than Mi, numerous serrations and strong ridges. _ Parectypodus 
II. Lower incisor compressed laterally, relatively larger, enamel 
(below tip) more or less limited to a band: 

A. Base of P4 notched. 

1. P4 longer than Mi, numerous serrations and strong ridges-. Neoliotomus 

2. P4 shorter than Mi, few serrations and feeble ridges Microcosmodon 

B. Base of P4 not notched. 

1. P4, longer than Mi, numerous serrations and strong ridges. Eucosmodon 

KEY TO AMERICAN GENERA OF TERTIARY PTILODONTIDAE (PJ) 

7. P* with two complete cusp rows and rudiments of a third Ptilodus 

77. P^ with only one complete cusp row, with rudiments of a second: 

A. Main cusp row rising posteriorly in an elevated point, noticeably 

anterior to the posterior end of the tooth base Ectypodus 

B. Main cusp row approximately horizontal, or arched: 

1. Cusps of main row heavier, fewer, rudiment of second row 

stronger Eucosmodon 

S. Cusps of main row smaller, more numerous, rudiment of 

second slight Neoliotomus 

[P* not known Parectypodus, Microcosmodon 



The known distribution is shown in table 8. 



Table 8. — Known distribution of American genera of Plilodontidae 



Genus 



Ptilodus 

Ectypodus 

Parectypodus 

Microcosmodon. . 

Eucosmodon 

Neoliotomus 



Paleocenk 



Lower (Puerco, 
lyower Fort 

Union of Clark 
Fork Basin) 



Middle (Torre- 
jon, Crazy Moun- 
tain Fort Union 
No. 2, Middle 
Fcrt Union of 
Clark Fork Basin) 



Upper 



A (Tiffany, Up- 
per Fort Union, 
Paskapoo) 



B (Clark Fork) 



Lower (Sand 

Coulee, Gray 

Bull) 



3' The distinction given may not be constant or really of generic value. The lower jaws of Ptilodus and 
Ectypodus show no clear generic distinction, although P< shows them to be quite separate, although closely 
related genera. 



82 



BULLETIN" 16 9, UNITED STATES NATIONAL MUSEUM 



Of the eight definable Fort Union species, only one, Ptilodus mon- 
tanus, can be placed with certainty as to genus. This is well known, 
from the entire dentition, and is so close to the genotype of Ptilodus 
that it certainly belongs to that genus. The species jepseni is excluded 
from all named genera but Parectypodus and Eucosmodon by the 
absence of a notch for P3. It does not resemble the type species of 
either of these genera very closely in the known parts (P4 and Mi), but 
it is somewhat closer to Parectypodus simpsoni and may be placed, 
very tentatively, in the same genus. Three species, silberlingi, 
russelli, and grangeri, have what seem to be the most distinctive lower 
jaw characters of the type of Edypodus, large length : width ratio of 
Ml (2.4 to 2.6 in these species, 2.5 in E. musculus), and large cusp 
number of Mi (total 14-17 in these species, 14 in E. musculus, typi- 
cally 9-10 in Ptilodus). They are therefore tentatively referred to 
Edypodus, although it is not probable that all belong to one genus or 
certain that any belongs to this genus. This leaves three species, 
sinclairi, gidleyi, and douglassi, which are tentatively placed in Ptilodus. 
The assignment is very uncertain in all three cases, and especially so for 
sinclairi, which, I suspect, may prove to represent a new genus when 
upper teeth are known, but no more probable position can be given 
them at present. 

As previously mentioned, with this material it is now impossible to 
recognize genera properlj^, and were it not for the requirement that a 
species be referred to some genus it would be m.ore satisfactory at pres- 
ent to consider all eight species (or the seven other than montanus) 
simply as species at large in the family Ptilodontidae. 

Table 9. — Comparison of lower dentition of I4 species of Ptilodontidae 



Species 



IPtUodus sindain 

f Edypodus silberlingi 

1 Par edypodus jepseni 

lEdypodus russelli 

? Edypodus grangeri 

T Ptilodus gidleyi 

t Ptilodus douglassi- 

Ptilodus montanus 

Ptilodus mediaecus 

Ptilodus irovessartianus 

Paredypodus simpsoni 

Paredypodus tardus 

Edypodus musculus 

Edypodus cochranensis 



Length 
Pi 



Mm 
3.1 
3.3 
4.3 
5.0 



5.3 
6.0 
6.6 
8.0 
8.3 
5.9 
4.2 
3.0 
4.0 
4.9 



Length 

Ml 



Mm 
1.9 
2.3 
3.1 
2.9 



3.4 
ca2.5 
3.7 
3.4 
3.5 
3.1 
2.3 
1.9 
2.5 



LP4 

LMi 



1.6 
1.4 
1.4 
1.7 



1.5 
ca2. 4 
1.8 
2.3 
2.3 
1.9 
2.0 
1.6 
1.6 



LMi 

WMi 



2.2 
2.6 
2.2 
2.5 



2.2 
2.0 
2.0 
1.9 
2.1 
2.4 
2.5 



Serra- 
tions 
Pi 



11.4 
12.0 
11.0 
14.0 



13.7 

14.3 

13.0 

13.8 

12.2 

13.8 

14 

10 

13 

14 



Cusps 
Ml 



6.6:4 
9.5:5.5 

7:6 
10.5:6.0 



LMi 
LM2 



1.9 
1.9 



1.8 
1.4 
1.4 
1.8 



Remarks 



No notch for P3. 

Notch for P3 more 
pronounced 
than in E. 
cochranensis. 



No notch for Pj. 
No notch for Pj. 



FORT UNION OF CRAZY MOUNTAIIsr FIELD, MONT. 



83 



COMPARISON OF SPECIES 

A summary comparison of the lower dentitions of the eight Fort 
Union species and the other known species of Ptilodus, Paredypodus, 
and Edypodus is presented in table 9. All figures are means, regard- 
less of the size or variability of the samples, which are, in most cases, 
noted elsewhere. Dimensions are in millimeters. The ratios are 
means of individual ratios, and not ratios of the means of the dimen- 
sions involved. Fractional serrations and cusps do not exist in the 
Taw data, but in some cases small or doubtful serrations or cusps have 
been counted as one-half. 

The known distribution of all American Tertiary species is shown in 
table 10. 



Table 10. — Known distribution of all American Tertiary species of Ptilodontidae 





San Juan Basin 


Clark Fork-Bighorn 


Crazy 

Moun- 
tains 


Al- 
berta 


Genera and species 


Puerco 


Torre- 
jon 


Tifiany 


Lower 

Fort 

Union 


Middle 

Fort 

Union 


Upper 

Fort 

Union 


Clark 
Fork 


Sand 
Cou- 
lee- 
Gray 
Bull 


Fort 
Union 
No. 2 


Paska- 
poo 


Ptilodus: 




















? 


mediaeviLS. . . 


X 
X 


X 


X 
X 


X 

X 
X 
X 




troressartianus 

montanus 




dougtassi. 




gidteyi.. 




sinclairi. .. 




spp. undetermined- 
Edypodus: 

■musculus 

grangen 


X 


X 




X 
X 
X 




russelli 

lilberlingi 




cochranevsis.- 

spp. undetermined. 
Paredypodus: 
simpsoni 


X 
X 


X 


X 


X 
X 


X 




tardus 




jepseni 




spp. undetermined. 




conus 


X 








americanus a 

a. primus.. 

molestus... 


X 
X 


X 
X 


X 


X 




teilhardi . . 




grattis 




sparsus... 








conventus .. 


x> 

X 




ultimus 





• Jepsen now believes (personal communication) that this is older, Paleocene. 



84 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

Genus PTILODUS Cope, 1881 

PTILODUS MONTANUS Douglass 

Figure 8 

Ptilodus montanus Douglass, 1908, p. 14; Gidley, 1909, p. 615; Granger and 

Simpson, 1929, p. 632. 
Ptilodus gracilis Gidley, 1909, p. 616; Granger and Simpson, 1929, p. 633; non 

Ptilodus gracilis (Marsh, 1889) Osborn, 1893. 
Ptilodus admirabilis Hay, 1930, p. 380, to replace Ptilodus gracilis Gidley, 1909, 

non Osborn, 1893. 

Type. — Carnegie Museum no. 1673, left lower jaw with P4 and Mi. 
Collected by A. C. Silberling. 

TyjJe 0/ Ptilodus gracilis Gidley. — U.S.N.M. no. 6076, skull, jaws, 
and partial skeleton. Collected by A. C. Silberling, 

Horizon and locality. — Fort Union no. 2, Middle Paleocene horizons, 
Crazy Mountain Field, Mont.. 

Diagnosis. — Length P4, mean 8.0 ±0.07, standard deviation 0.42 ± 
0.05. Length Mj, mean 3.4 ±0.07, standard deviation 0.20 ±0.05. 
Length P*, mean 5.5±0.11, standard deviation 0.38±0.08. Width 
P^ mean 2.6 ±0.06, standard deviation 0.22 ±0.04. Ratio length 
P4 : length Mi, mean 2.3 ±0.02, standard deviation 0.04±0.0L Ratio 
length Ml : width Mj, mean 2.0±0.04, standard deviation 0.13 ± 
0.03. Serrations P4 13-15, mode 14. Cusps P^ 4-7, mode 6. Outer 
cusps P* 0-3, mode 0. Inner cusps P^ 9-10, mode 9. Outer cusps 
M^ 7-9, mode 8. Cusps Mi external 5-6, mode 6, internal 4-5, 
mode 4. 

Discussion. — This is far the commonest single species in the fauna. 
The type happens to be almost exactly at the mean or mode for every 
character that it shows, and hence it is extraordinarily well fitted to 
be the type, although this was, of course, accidental, as it was almost 
unique when described. Gidley distinguished his Ptilodus gracilis as 
being slightly smaller than P. montoMus, lower jaw far more slender, 
and five outer cusps on Mi as against six in P. montanus. The other 
characters given were, as Gidley recognized, not comparable with or 
not distinctive from P. montanus. Mi appears to me to have six 
external cusps, rather obscured by wear.^^ The slight size distinctions 
are not valid specific characters, for now that the whole collection 
can be compared it is seen that P. gracilis Gidley falls definitely 
within the range of P. montanus in every respect. It happens to 
be one of the smallest specimens of tliis species, and this unfortunate 
chance, not recognizable as such when he wrote his preliminary 
paper, misled Gidley into thinking it representative of a separate 
species. 

3' The presence of only five would not necessarily be distinctive anyway, as one specimen, surely of 
montanus, has only five and two others have five large cusps and one small and indistinct. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



85 



The circumstance that the two previously named species of Fort 
Union ptilodonts are synonymous makes of no interest the question 
whether Osborn's incorrect reference of Cimolomys gracilis Marsh to 
Ptilodus invahdates Gidley's later Ptilodus gracilis and robs Hay's 
name Ptilodus admirabilis of any raison d'etre. 

The distinction of this species from the very closely related Ptilodus 
mediaevus of the Torrejon has already been discussed in part as exem- 
plifying the methods used in this research. The more important 
comparisons may be summed up as follows: 




Figure S.— Ptilodus montanus Douglass, U.S.N.M. no. 6076, left lower jaw (with some details completed 
from right lower jaw of same individual): a. External view; 6, crown view. Three times^natural size. 

Most dimensions not significantly different, but in the one specimen 
of P. mediaevus that has this tooth the deviation of the width of P^ 
from the mean in P. montanus is 2.7 times the standard deviation of 
the latter. 

Serrations of P4, mode 14 in P. montanus, and of six specimens of 
P. mediaevus five have 12 and one 13. 

Cusps of P^, mode 6 in P. montanus, and of three specimens of P. 
mediaevus two have 4 and one 5. 

External cusps of P*, mode in P. montanus, and one specimen of 
P. mediaevus has two. The development of this external shelf is 
stronger in this specimen of mediaevus (and in another in which the 
cusps cannot be surely counted) than in any specimen of montanus. 



86 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

It is this character also that is reflected in the greater width of this 
tooth in mediaevus. Median cusps of P^ not significantly different, 
but internal cusps mode 9 in montanus, and 8 in one specimen of 
mediaevus. 

The two species are certainly very closely related, but cannot be 
considered synonymous. 

No other described species could be confused with P. montanus. 

Thanks to the fine specunen found by Silberling and prepared and 
described by Gidley, Ptilodus montanus is the best-known multituber- 
culate and typifies this order, the longest lived and among the most 
widespread of all mammalian orders, despite its extinction in the 
Lower Eocene. Gidley (1909) published an excellent, but explicitly 
provisional and preliminary, description of the best specimen, and it 
was later redescribed summarily, with new reconstructed sketches, by 
Broom (1914). It has become a classic specimen and is mentioned in 
practically all and figured in many of the general works on fossil 
mammals (e. g., Schlosser, 1923; Osborn, 1910; Romer, 1933; etc.; 
Scott, 1913, adds a life restoration, and Abel, 1912, a modified but 
incorrect reconstruction based on Gidley 's figures). 

The species is here briefly redescribed, as typical of family and order 
(or at least suborder). By taking into consideration numerous other 
specimens of this species, and with the help of more recently described 
specunens of other species, it is possible to add a few points to those 
previously described and also to remove the discrepancies involved in 
the previous descriptions. 

Dentition. — The dental formula is rMl- Gidley gives yjM- He 
considered the second upper tooth as a canine, but it is surely an 
incisor. His inclusion of a lower canine is doubtless a lapsus calami, 
as there is no suggestion of such a tooth, and he does not mention it 
in his description. His premolar-molar division seems to me to be 
the most suitable one, although the real criterion, replacement, is not 
available. The ancestors of Ptilodus probably had five upper pre- 
molars, but it is uncertain which one was lost, and hence it is conven- 
ient to call those of Ptilodus simply P^''*. Its lower premolars, how- 
ever, are certainly P3.4 of the ancestral series and are so designated. 

I^ is a large, high-crowned, but apparently rooted tooth with a 
completely enameled crown. It is directed downward, forward, and 
inward, so that the tip must have been nearly in contact with that 
of its mate on the other side, although the alveoli were well spaced. 
The anterior face is convex and the posterior concave vertically and 
slightly convex transversely except for excavations at the sides. 
There are sharp vertical external (proximal) and internal (distal) 
crests, and near the tip is a more rounded posterior (lingual) crest, 
so that the tip is triangular in section. There are no accessory cusps. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 87 

I^ is apparently present in only one specimen, the most complete 
one, no. 6076, and here I suspect that it is incorrectly shown. The 
tooth inserted in this position is an incomplete crown, with no root, 
bedded into the broken I^ alveolus in plaster. In size and structure 
it is exactly a mirror image of the same part of the I^ of the same side, 
right, which seems almost conclusive evidence that it is, in fact, the 
left I^ that was loose in the matrix and was erroneously inserted in 
this position. If this is true, I^ is still unknown in this species.^^ 

I^ and I- were well spaced, and another diastema of about equal 
length lies between I' and P^ The latter tooth is tricuspid in all 
specimens, with tliree equal cusps, one anterior and a transverse pair 
posterior. P^ is also constant in cusp structure and resembles P^ but 
is wider and quadrate, with four cusps, two transverse pairs. P^ is 
narrower than the adjacent teeth and as shown elsewhere is extremely 
variable in size and in construction. There is little doubt that it is 
in process of reduction and that its great variability is a feature of 
degeneration.^^ The cusps are similar to those of P^~^ but smaller and 
more variable. There are always two transverse pairs, and on the 
bulging anterior and posterior basal parts others may be developed. 
When present, these are usually anterior, one or a pair, but in two 
specimens there is also a cusp posterior to the constant four. 

P^ the upper shearing tooth, is much enlarged and has a plane, 
slightly inclined inner face. The internal cusp row consists of numer- 
ous small cusps (full data on cusp number are given elsewhere), united 
nearly to their apices and arranged in a straight anteroposterior hne. 
External to this is another row, slightly shorter posteriorly, somewhat 
curved (convex externally), with fewer, larger, and more separated 
cusps. On the anterior part of the external face of the tooth the base 
bulges outward, forming a shelf which is usually vaguely papillate, 
without distinct cusps, but may have one or more cusps. 

The premolar cusps are all similar, nearly conical, sharply pointed, 
the enamel furrowed and ridged radially from the point, one to three 
of these ridges developed into more prominent, sharp crests. 

M^ has three cusp rows, and these are of nearly equal length when 
unworn. The internal row, however, narrows anteriorly. All its 
cusps are relatively smaller, and anteriorly they become numerous and 
minute. This anterior part may be shorter than the other rows, but 
it is invariably sheared off very early in life by backward movements of 
P4. The middle and outer cusp rows are of equal width and cusp size 
throughout, and the two are of about equal length. The cusp form is 

38 The error, if such it be, is a very natural one, especially as the tooth may have lain near the alveolus 
since the fragments of this specimen are very much disturbed in the matrix. Gidley notes the resemblance 
of the tooth to I' except for the apparent reversal of inner and outer sides. His statement that it is smaller 
is true only of the apparent height, and the tooth is brolcen and the true height not shown. 

3' Reduction in the midst of the premolar series rather than at its ends may be characteristic of m.ulti- 
tuberculates. In the Plagiaulacidae of the Jurassic, it seems to be the third of the five premolars that is 
being reduced, and hence the ptilodontid premolars may be P'"' and P*"' of the ancestral series. 

119212—37 7 



88 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

complex. The external cusps are rounded on the external face and 
have the more flattened internal face marked by a few deep radial 
furrows and intervening ridges. The internal cusps are simpler but 
tend to develop the same form, the furrowed side being external 
(toward the middle of the tooth in both cases). The cusps of the 
middle row are vaguely crescentic, the anterior face somewhat con- 
cave and the posterior convex, with the two sides flattened and 
furrowed. 

M^ is much shorter and very slightly wider than M'. Internal and 
median rows are of about equal length, but the cusps of the middle row 
are larger, fewer, higher, and more separate. They are more distinctly 
crescentic than on M\ The outer row is confined to the anterior half 
of the tooth and generally has a single crest and outer surface, so that 
separate cusps cannot be distinguished. 

The sole lower incisor is a long, slender, curved, scimitarlike tooth 
with a completely enameled crown, the enamel thin on the postero- 
basal part and there not extending so far down. The anteroexternal 
face is smooth and convex, and there is a sharp anteromedial (or 
buccodistal) crest, next to which the internal face is excavated. There 
is a much weaker and shorter but similar posteroexternal (bucco- 
proximal) crest. The long, but closed, root is inserted in a heavy 
collar of bone. 

Ii is followed by a long diastema, and homologues of Pi. 2 of the 
Plagiaulacidae are absent. P3 is a tiny, 1 -rooted, styliforra tooth, 
nearly circular in horizontal section, inserted vertically under the an- 
terior edge of P4 in such a way that its crown fits tightly into a notch 
in the base of the latter. The crown is slightly expanded and bulbous 
and is enameled on the anterior face. The tooth has no function save 
that of buttressing P4. 

P4 is the famihar large shearing tooth, which reaches its greatest 
known development in this genus. It has been so often described and 
so well figured as to require no detailed description here. Mi is a long, 
narrow tooth with two cusp rows. The cusps resemble those of the 
external and internal rows of M^ but tend to be very vaguely crescen- 
tic, concave on the posterior surfaces. M2 is wider but much shorter. 
The cusps are larger but less separated, in each row, and the median 
valley is wider and more open. The external cusp row generally ex- 
tends farther posteriorly than the internal. This tooth seems to suffer 
more severe wear than does Mi. 

Skull. — Seen from above, the skull is almost perfectly triangular 
except for the slight concavity in outline anterior to the zygoma. The 
orbits are almost exactly median. The skull proper is broadest, and 
about equally broad between the anterior and between the posterior 
zygomatic roots, that is, between the anterior edges of the orbits and 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 89 

across the cerebellar region. The postorbital constriction is very 
slight and postorbital processes are lacking. 

The complete, sigmoid zj^goma arises nearly at the middle of the 
palatal region, opposite P^~*. 

The most striking characteristic of general outline is the extremely 
posterior position of the glenoid surfaces, wliich extend almost to the 
plane of the occiput, so that the basicranial region is remarkabl}'^ 
short and wide. There are no pre- or post-glenoid and probably no 
paroccipital processes. The vnde occipital condyle has a cochleate 
surface, its ventral exposure larger than the posterior. 

The nasals, which are unfused, are broad, stout bones. They are 
slightly constricted near their middle portion, and expanded posteri- 
orly. The nasofrontal suture, slightly curved so that the frontals are 
inserted into a broad and very shallow notch between the nasals, 
almost exactly touches at its most posterior point a line joining the 
most anterior margins of the two orbits. There are several small 
foramina in the nasals, the most prominent a pair, one near the middle 
of the posterior half of each nasal. 

The premaxillae show no characters of interest. Their posterior 
facial sutures cannot be made out, or the extent of their palatal 
expansion, although they meet at the midhne as far back as the anterior 
end of I^. 

The maxilla is a relatively very large bone. It has a small frontal 
contact above the anterior rim of the orbit. *° It forms the whole 
anterior root of the zygoma and apparently at least half of the zygoma 
itself. I can detect no jugal. It may have existed as a slender bone 
above the zygomatic portion of the maxilla, as shown in Broom's 
restoration, but this is purely hypothetical. No. 9710 has the zygoma 
nearly complete, although fractured and dislocated, and in it no jugal 
is visible, so that it is quite possible that this bone was wholly lacking 
or fused with the maxilla. On the palate, the maxiUae form a strong 
transverse bridge, principally between P^~^ of opposite sides. Anterior 
to this in the midline they form a pointed process between the anterior 
palatal foramina, which are very large and lie between but in greater 
part posterior to the second incisors. Posterior to the transverse 
palatal bridge of the maxillae is a slender median bar between the 
vacuities, but whether this is formed by the maxillae, palatines, or 
both cannot be made out. Broom (1914, p. 123) has mentioned that 
"the front part of the maxilla is curiously excavated as if it retained a 
large nasal floor cartilage." The excavation opens at the postero- 
lateral side of the anterior palatal foramen and is cut off from the 
nasal passage proper by a flange of bone from the maxilla. As shown 

'" Broom (1914) shows maxilla and frontal separated by a small lacrimal, but this is hypothetical (dotted 
lines on his drawing). In fact, no lacrimal is distinguishable, and there does appear to be a definitely visible 
frontomaxillary contact on the right side. This region is known in several multituberculates, and none 
shows a lacrimal, at least outside the orbit. Probably this bone is lacking or irtracrbital in this order. 



90 BULLP^TIN 16 9, UNITED STATES NATIONAL MUSEUM 

in another specimen (no. 9762) it runs backward into the maxilla for a 
short distance and ends in a blind point. An alternative, and I 
think slightly more probable, explanation is that this peculiar pocket 
lodged a nasal diverticulum. The large paired palatal vacuities, 
regularly long and elliptical in outline, extend from opposite the 
posterior end of P- to the anterior end of M^*^ 

As shown vaguely in the best skull and definitely in no. 9710, the 
maxillopalatine suture parallels the dental border and ends anteriorly 
at the rim of the vacuity opposite the anterior end of M^ The 
palatines thus form the whole of the quadrangular palatal bridge 
principally between the first molars. In no. 9762 this is seen to be 
pierced on each side by a long, large, horizontal canal opening anteri- 
orly at the vacuity and posteriorly in the basicranial region, perhaps 
in the choanae. The posterior palatal rim is slightly thickened. 

The choanae are completely separated by a thin, vertical, median 
plate of bone, probably the vomer, as suggested by Broom. The 
palatopterygoid crests are low and rounded and do not extend down- 
ward to the level of the palate. There apparently was no hamular 
process. 

The frontals are fairly large and cover most of the interorbital 
region and form the superior border of the orbits. There are thin 
lateral forward extensions of the parietals, which lap over the frontals, 
as correctly shown by Broom, but they do not reach the nasals or 
maxillae as in Taeniolabis. 

The anterior branches of the sagittal crest nearly follow the parieto- 
frontal sutures, and the crest becomes single only near the junction 
with occiput and is there low. The parietals are fused on the midline, 
in distinction from the nasals and frontals. The presence of an inter- 
parietal, as shov/n in broken lines by Broom, is purely hypothetical. 
The parietosquamosal suture is not determinable. The large un- 
broken piece of bone on the left side does not show it, and this suggests 
that the posterior end of the suture was more lateral, and the parietal 
here broader, than shown in Broom's restoration. 

The squamosal forms the posterior portion of the zygoma. Anterior 
to the glenoid surface its lower face is slightly excavated, and this 
may have been for the jugal, as suggested by Gidley and tentatively 
shown on Broom's restoration, but this is by no means certain and 
seems to me improbable. The glenoid surface, in any event, is wholly 
on the squamosal and is oval and nearly plane. From it the squamosal 
swings almost straight medially to the lambdoid crest. 

The basicranial region is very obscure, but a few details can be 
made out. The anteroventral part of the occipital condyle is a very 
thin flange underhanging a pocket in the posterior part of which is 

" They are considerably too short in Broom'srestoration, the anterior margin being placed too posteriorly. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 91 

the condylar foramen, apparently single as Broom says, although a 
second opening may possibly have occurred along an adjacent broken 
area. 

Farther anteromedial is another foramen, opening into a canal run- 
nmg forward, probably for the carotid. Between these and the 
temporal fossa is an elliptical opening on the skull as preserved elon- 
gate anterointernal-posteroexternallj'. There is some bone exposed 
at the posteroexternal end of this, not far from the posterointernal end 
of the glenoid surface. This doubtless belongs to the auditory appara- 
tus, but I cannot identify the elements. How this opening may have 
been floored is not determinable, but I agree with Broom and differ 
from Gidley in finding no evidence that there was an alisphenoid bulla. 
Part of the bony internal wall of the vacuity is broken, revealing that 
it contains a relatively large, gently curved, cavity, interpreted by 
Broom as an uncoiled cochlea, a possible but not certain interpretation. 
The anteroexternal rim of the vacuity is formed by a ridge continuous 
anterointernally with the pterygopalatine crest, and posteroexternally 
with the squamosal stalk attaching the glenoid (and zygoma). In 
the lower surface of this ridge near its junction with the pterygopalatine 
crest is a distinct foramen. Immediately above this, more in the 
lateral cranial wall, is apparently another foramen, directed forward 
and downward. The first of these openings does not, as Gidley 
believed,^^ lead to an alisphenoid canal, and the two foramina together 
probably represent the foramen ovale. Above and somewhat posterior 
to the end of the palate, in the lateral cranial wall, is a large anterior 
lacerate foramen. Separate rotund or optic foramina cannot be dis- 
tinguished, and they are probably confluent with this fissure. More 
anterior, at the same or a slightly higher level, above the anterior end 
of M\ is a smaller foramen, probably the ethmoid or sphenopalatine 
foramen. 

Mandible. — The rodentlike form of the mandible is well shown in 
the figures. The symphysis is unfused.*^ The coronoid process is 
feeble, somewhat recurved, and possibly pointed — it is not quite com- 
plete in any specimen. The masseteric fossa is deep and bounded by 
a strong flaring flange below. The pterygoid fossa is still more pro- 
nounced and the pterygoid crest still more flaring. There is no angular 
process. The dental foramen is at the bottom of the deep pterygoid 
fossa, and the very small mental foramen is beneath the diastema. 

Vertebrae. — There are several vertebrae, but they are so poorly pre- 
served that little can be made out beyond the suggestion, already 
noted by Gidle}^, that neck and tail were both long and heavy. 

" He said (1909, p. 619), "there appears to be an alisphenoid canal", and I assume that he was referring 
to this opening. 
" Apparently it never fused in any multituberculate. 



92 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

Humerus. — The head is large, oval, anteroposterior diameter slightly- 
greater than transverse diameter. The trochanters are not preserved. 
The shaft is slender, deltoid crest present but weak. The entepicon- 
dyle, slightly broken, is large, and the foramen present but small. The 
external side of the distal end is broken, and the ectepicondylar region 
is not preserved. What remains of the radial articulation suggests 
that it was nearly spherical. The trochlea is not a broad groove 
bounded by a sharp crest as in later mammals (except monotremes, 
in which, however, these articulations are still less Ptilodus-Y^ke, than 
are those of primitive Theria) but forms another subspherical, slightly 
crested, condyle. The fossa for the olecranon is sharp and deep. 

Ulna. — The proximal end of the ulna has a nearly round, concave 
articular surface. The shaft is stout, with a strong biceps insertion. 
The distal end, which lacks the epiphysis, is widely expanded. 

Pelvis. — Broom (1914) interpreted what Gidley took for the pelvis 
as a shoulder girdle and restored it in such a way as closely to resem- 
ble the monotreme shoulder girdle, but Granger added a note to 
Broom's paper (at Broom's request) pointing out that Gidley's opinion 
was correct. This was based on the fine Eucosmodon material later 
described by Granger and Simpson (1929) and by Simpson and Elft- 
man (1928). There can be no doubt that the element is a pelvis, 
although it is so extraordinary that Broom's error was quite under- 
standable.^ The detailed descriptions of the Eucosmodon jjelvis 
already published make it unnecessary to go into any detail regarding 
that of Ptilodus. k.^ far as one can judge from the imperfect material, 
the two are closely similar throughout, except that in Ptilodus the 
pelvis is slenderer, with weaker muscle origins. 

Femur. — The femur of Ptilodus is also much like that of Eucosmodon, 
except for being smaller and relatively weaker. The great trochanter 
does not rise so far above the head, and the lesser trochanter is rela- 
tively a little smaller, with less expanded head. 

Tihia andjibula. — These bones are poorly preserved and show Httle 
except their relative sizes and the remarkably deep posteroproximal 
excavation of the shaft, as in Eucosmodon. 

Measurements of the two types included here and the most important 
statistical data follow. Here, and elsewhere, I do not give all the 
many measurements on which these figures depend. The data are 
given in a form that shows all the essential and few or no nonessential 
figures and that makes comparison much easier and more reliable than 
the publication of long tables of raw data, 

" In Gidley's figure (1909, fig. 4) the pelvis is restored by analogy with marsupials. The Eucosmodon 
specimen shows this restoration to be incorrect. 



FORT UNIOX OF CRAZY MOUNTAIN FIELD, MOXT. 93 

Table 11. — Measurements of Ptilodus naontanus: Continuous variates 



Variate 


X 


R 


U 


cr 


V 


LP4 

LMi 

LP3 

WP3 

LP^ . - -- 


36 

9 

21 

21 

12 

12 

9 

6 

9 


7. 1 -9. 1 

3. 2 -3. 7 
2. 6 -3. 4 
2. -2. 6 

4. 8 -6. 
2. 1 -2. 9 
4. 2 -6. 
2. 25-2. 40 
1. 8 -2. 2 


8. 04 ±0. 07 
3. 44 ± 0. 07 
2.97 ±0. 12 
2. 29 ±0.03 
5. 50 ±0. 11 
2. 62 ±0. 06 
5. 03 ±0. 17 
2. 330±0. 018 
1. 98 ±0.04 


0. 42 ± 0. 05 
0. 20 ±0.05 
0. 55 ±0.08 
0. 150 ±0.023 
0. 38 ±0.08 
0. 22 ±0.04 
0.50 ±0. 12 
0.045 ±0.013 
0. 13 ±0.03 


5. 3±0. 6 

5. 7±1. 4 
18. 5±2. 8 

6. 6±1. 
6 9±1 4 


WP*. 


8 4±1 7 


LMi 

LP4:LMi 

LMi:WMi 


10. 0±2. 4 



Table 12. — Distributions of discontinuous variates: Ptilodus montanus 



Serrations P4 



13. 
14. 
15. 



.-8 

.19 

2 



External cusps Mi : 
Internal cusps Mi : 



External cusps M2: 4 5 

Internal cusps M2 : 2 4 



Cusps P3:< 



External cusps P-* : 



--3H 
_._5» 
.lOH' 
-__li 

...3 

--I/2 
---Vz 



5 1 

6 4 

Median cusps P'':^- * „ 

2 



f 9 . 7 

Internal cusps P*o,f^ ' o 

(t/.".::::::;-"" 

External cusps Mi:-^8 



Median cusps M' 



..1 

6>$ 

-V2 
5% 
..2 



Median cusps M^: 3 4 

'3 2 

4 2 



Internal cusps M^ ; 



• In all the teeth with five cusps and in all but one with six, the cusps additional to four are evidently 
anterior, but in one with six there is an extra anterior and an extra posterior cusp. The tooth with seven 
cusps has two extra anterior cusps and one extra posterior. 

' That is, a slight bulging shelf, generally vaguely papillate, but without distinct cusps. 

The internal cusps of M^ are invariably sheared by P4 at the anterior 
end and cannot be accurately counted in any specimen. Failure to 
recognize this would lead one to believe the various stages of wear 
typical of different species, if not genera. The outer cu.^ips of M^ are 
also too obscure to count in the available specimens. 

Tliis species is abundant both in the Gidley and Silberling Quarries, 
where its remains are among the commonest and are the best preserved 
of all the fossil mammals. No significant difference can be observed 
between the specimens from the two quarries, and the preceding data 
are based on the combined sample from both. Two specimens surely 
of this species were found at Loc. 50, and a broken P4 from Loc. 51 
probably belongs to it. 



94 



BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



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FORT UXIOX OF CRAZY MOUNTAIN FIELD, MONT. 9o 

rPTILODUS DOUGLASSI Simpson 

Figure 9, a 

?Ptilodus douglassi Simpson, 1935d, p. 225. 

Type. — U.S.N. M. no. 9795, right lower jaw with P4-M2. Collected 
by A. C. Silberhng. 

Horizon and locality. — Gidley Quarry (and two referred specimens 
from Silberling Quarry), Fort Union, jSIiddle Paleocene horizon, 
Crazy Mountain Field, Mont. 

Diagnosis. — Mean length P4 (three specimens) 6.6, deviation from 
mean of P. montanus —1.4, 3.3 times standard deviation of the latter. 
Length Mi (type) not significantly deviating from that of P. montanus. 
Katio length P4: length Mi (type) 1.8, deviation from mean P. mon- 
tanus — 0.5, 12.5 times standard deviation of the latter. Length 
Ml '.length M2 (type) 1.8, deviation from mean P. montajius-i-OA 
(standard deviation not calculable, but difference almost certainly 
significant). Serration and cusp number not significantly different 
from P. montanus. 

Remarks. — Expressed in other and less definite words, the species 
is structurally closely similar to P. montanus but differs significantly 
in its smaller size, relatively much smaller P4, and relatively smaller 
M2 (or, much larger Mi relative to P4 and Mo). P4 also appears to be 
somewhat lower in lateral contour, but this cannot be adequately 
checked . 

No species other than P. montanus resembles this closely enough 
to demand further comparison. 



Table 14.- 


-Measurements 


of in 


divid 


jial specimens 


of Ptilodus douglassi 




LPa 


M, 


Mj 


LP4 
LM, 


LM, 
WMi 


LM, 
LMj 


Serra- 
tions 
P< 


Cusps 
Ml 


Cusps 


U.S.N.M. no. 


L 


W 


L 


w 


M, 


9793 


Mm 
6.5 
6.6 
6.8 


Mm 
3.7 


Mm 

1.7 


Mm 
2.C 


Mm 
2.1 


1.76 


2.2 


1.8 


13 

?13 

13 


6:4 


4:2 


988Sa 




9888b 





































7PTILODUS GIDLEYI Simpson 

Figure 9, h 

IPtilodus gidleyi Simpsox, 1935d, p. 225. 

Type.— U.S.N.A'I. no. 9763, left lower jaw with P4 and broken Mi. 
Collected by A. C. Silberling. 

Horizon and locality. — Gidley Quarry, Fort Union, Middle Paleocene 
horizon, Crazy Mountain Field, Mont. 

Diagnosis. — Length P4, type, 6.1 (two other specimens 5.9 and 6.1). 
Length Mi, type, about 2.5. Ratio length Piilength Mj about 2.4, 



96 



BULLETIN 169, UNITED STATES NATIONAL MUSEUM 



that is, not significantly different from P. montanus or mediaevus but 
much higher than in any other known species of this or closely related 
genera. Serrations P4, type, 14 (two other specimens 14 and 15). 
P4 very short and high in lateral contour, rising well above the grinding 
plane of Mj. 

Remarks. — Except for its somewhat more elevated P4, this closely 
resembles P. montanus in its Icnown proportions and other morpho- 
logical features, but it is much smaller (deviation of length P4 from 
mean of P. montanus —2.0, nearly five times standard deviation of the 
latter), too much so to consider it a small variant of montanus, despite 
the considerable variabilitv of the latter. 






Figure 9. — Ptilodus, comparative outline drawings of lower dentition: a, P. douglassi Simpson, U.S.N.M. 
no. 9795; b, P. gidleyi Simpson, U.S.N.M. no. 9763; c, P. sinctairi Simpson, U.S.N.M. no. 9770. Crown 
and external views, all drawn as if left lower jaws (a and c reversed from right lower jaw). Three times 
natural size. 

P4 of this species is of the same size as in P. trovessartianus. Ma- 
terial is insufficient for full analysis, but if we assume the variability 
of both not to be much greater than in P. montanus, the shorter Mi 
of ?P. gidleyi*^ and the resulting larger ratio length P4: length Mi 
are surely significant. These same differences distinguish it even 
more sharply from the somewhat larger species ?P. douglassi. No 
others resemble it closely. 

Table 15. — Measurements of individual specimens of ?Pti]odus gidleyi 



U.S.N.M. no. 


LP, 


LMi 


LP, 

LM, 


Serrations 
P, 


Cusps Mi 


9802 


Mm 
6.9 
6. 1 

6.1 


Mm 




15 
14 
14 




9763 - -- 


ca. 2. 5 


ca. 2. 4 


?6:? 


9764... 













«' This is not exactly determinable from the specimen, but the error of measurement can hardly exceed 
0.2 mm and is almost surely less. Alveoli in a referred specimen also indicate a very short Mi. 



PORT UXIOX OF CRAZY MOUNTAIN FIELD, MONT. 97 

An isolated P4 from Loc. 50 (American Museum collection) measiires 
6.1 mm in length, has 15 serrations, and closely resembles the type of 
this species in form. There can be little question that it belongs here, 
as it is so close to the known mean for this species and far outside the 
range of any other species recognized in this field. 

7PTILODUS SINCLAIRI Simpson 

Figure 9, c 

tPlilodus sinclairi Simpson, 1935d, p. 225. 

Type.— U.S. ^.M. no. 9770, left lower jaw with P4-M2. Collected 
by A. C. Silberhng. 

Horizon and locality. — Gidley Quarry (referred specimens from 
Silberling Quarry), Fort Union, Middle Paleocene horizon, Crazy 
Mountain Field, Mont. 

Diagnosis. — Length P4, mean 3.1 ±0.07, standard deviation 
0.29 ±0.05. Length Mi, mean 1.9 ±0.03 standard deviation 0.08. 
Ratio length P4: length Mi, mean 1.6 ±0.08 standard deviation 0.22 ± 
0.06. Ratio length Ml : wddth M], mean 2.2 ±0.06, standard devia- 
tion 0.17±0.04. Serrations P4 10-13, m.ode 12. Cusps Mi 6-7:4, 
mode 7: 4. 

Remarks. — Some of the peculiarities of this species, second only to 
P. montanus in abundance, have already been discussed above. Its 
very small size at once distinguishes it from any species of related 
genera except lEdypodus silberlingi (diagnosed below), and Parecty- 
podus tardus, with which it cannot be congeneric, as it has P3. 

The two specimens (6089 and 6090, and also a third, 6149, so labeled 
but not published by number) that Gidley at first (1909, p. 623) re- 
ferred to "Ptilodus formosus'^" (Marsh) {=Halodon jormosus Marsh) 
belong to IPtilodus sinclairi.*^ Adequate comparison with the frag- 
mentary Cretaceous types of Marsh is impossible, but in view of the 
very different age and of the fact that when close comparison is pos- 
sible not only the species but also the genera are very distinct, it may, 
I think, be assumed that the Fort Union forms do not belong to 
Cretaceous species. 

As noted above, it is improbable that this species belongs to Ptilodus, 
but it cannot at present be clearly distinguished from that genus. 

«5 Gidley did not change their labels, but it is practically certain that he recognized their pertinence to a 
distinctive species. He recognized tPlilndun sinclai-i (under a different, unpublished name), and so labeled 
about half the specimens that I place here, covering almost the same ranse of variation, so that in this ease 
his specific criteria and mine lead to nearly the same result. Ee also included, however, one or two speci- 
mens that I place in other species. 



98 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

The principal numerical data on this form are as follows: 
Table 16. — Measurements of ?Ptilodus sinclairi: Continuous variates 



Variate 


N 


R 


M 


a 


V 


LP4 

LMi 


16 

8 
8 
8 


2. 5-3. 7 

1. 7-2. 

1. 32-1. 95 

1. 9-2. 4 


3. 13 ±0. 07 

1. 88 ±0.03 

1. 61 ±0. 08 

2. 25 ±0. 06 


0. 29 ±0. 05 
0. 083 ±0.021 
0. 22 ±0.06 
0. 17 ±0. 04 


9. 3±1. 6 

4. 4±1. 1 


LP4:LMi 

LMi:WMi.__ 





Table 17. — Distributions of discontinuous variates: ?Ptilodus sinclairi 



Serrations P4:. 



External cusps Mi:. 



10. 
11. 

113- 
6. 



Internal cusps Mi: 4 7 

External cusps M2: 4 3 

Internal cusps M2: 2 3 



[7.. ..4 

Table 18. — Measurements of individual specimens of ?PtiIodus sinclairi 



U.S.N.M. 


LP4 


M, 


Ml 


LP, 
LMi 


LM, 
WMi 


LM, 
LM2 


Serra- 
tions 
Pi 


Cusps 
Mi 


Cusps 


no. 


L 


W 


L 


W 


M2 


9797 


Mm 
2.6 
2.9 
3.3 

3.7 


Mm 
1.9 
1.9 
1.7 
1.9 


Mm 
0.8 
0.8 
0.9 
0.8 


Mm 
0.9 
1.1 
0.9 
0.9 


Mm 
0.9 
0.9 
0.8 
0.9 


1.37 
1.53 
1.94 
1.95 


2.4 
2.4 
1.9 
2.4 


2.1 
1.7 
1.9 
2.1 


10 
12 
11 
12 


7:4 

? 

6:4 

6:4 


4:2 


9792 . 


? 


9770 _. 

9791.. 


4:2 
4:2 







These four best specimens include practically all the extremes in 
these characters. 

A P4 collected by A. C. Silberling on January 21, 1903, now in the 
Princeton University collection, measures 3.0 mm in length and has 
12 clear serrations and 1 obscure. It is indistinguishable in any way 
from some of the smaller variants of Ptilodus sinclairi from the Gidley 
Quarry and is referred to that species. Nothing like it has been dis- 
covered at a Lower Paleocene horizon, nor is it exactly matched in 
any of the many Lance specimens (Cimolomys, sensu lato) known to 
me. It bears the horizon designation "Puerco" (by which was then 
meant approximately the series later called Fort Union No. 1), the 
number 14, and the locality ''Moen and Beck" (a very general locality 
including a large area along Bear Butte). Mr. Silberling informs me 
positively that this is from Loc. 65, and this can be taken as correct. 
The specimen is thus the oldest mammal ever found in this field. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 99 

Genus ECTYPODUS Matthew and Granger, 1321 

7ECTYPODUS GRANGERI Simpson 

Figure 10, a 
lEctypodus grangeri Simpson, 1935d, p. 226. 

Type.—U.S.ISIM. no. 9801, left lower jaw with P4-M1. Collected 
by A. C. Silberling. 

Horizon and locality. — Gidley Quarry, Fort Union, Middle Paleocene 
horizon, Crazy Mountain Field, Mont. 

Diagnosis. — Length P4, type and mean of four specimens, 5.3. 
Length Mi, type and mean of three specimens, 3.4. Ratio length P4: 
length Ml, type 1.56, referred specimen 1.53. Length Mi: width Mi, 
type 2.6, mean of three specimens, 2.4. Serrations P4, tj^pe 14, other 
specimens, two 14, one 13. Cusps Mi, type, 8:7, other specimens one 
8:7, one 8:6. Apex of P4 nearly on a level with grinding surface of 
Ml. 

Remarks. — Like the other two new species tentatively referred to 
"LEctypodus, below, this differs from all species referred to Ptilodus in 
the large length: width ratio and large cusp number of Mi, characters 
that appear to be surely significant and make closer comparison with 
species of Ptilodus unnecessary. This, and the next two species, are 
excluded from Parectypodus by the presence of P3. 

The present form compares very closely with Ecfypodus musculus in 
all its visible characters. In spite of the small size of the samples, the 
considerably greater size of ?E. grangeri is almost certainly significant, 
and its association with wide geographic separation and with a dis- 
tinct difference in age shows the species to be distinct. 

The principal measurements are given in table 19. 



Table 19. — Measurements of 


individual 


specimens of 


?Ectypodus grangeri 


U.S.N.M. 


LP4 


M, 


LP4 

LMi 


LM, 
WMi 


Serra- 
tions 
Pi 


Cusps 


no. 


L 


w 


Mi 


9800 


Mm 
5.2 
5.3 
5.4 
5.4 


Mm 
3.4 
3.4 


M7n 
l.G 
1.3 


1.53 
1.56 


2.1 
2.6 


14 

14 
13 
14 


8:6 


9801 


8:7 


9773 




9782 












9771 


3.3 


1.3 




2.5 


8.7 











7ECTYPODUS RUSSELLI Simpson 

Figure 10, b 
lEctypodus russelli Simpson 1935d, p. 226. 

Type.—U.S.'N.M. no. 9765, left lower jaw with P4-M2. Collected 
by A. C. Silberling. 



100 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

Horizon and locality. — Gidiey Quarry, Fort Union, Middle Paleo- 
cene horizon. Crazy Mountain Field, Mont. 

Diagnosis. — Length P4, type and mean of three, 5.0. Length Mi, 
type and referred specimen, 2.9. Ratio length P4: length Mi, type 
and referred specimen, 1.7. Length Miiwidth Mi, type 2.4, referred 
specimen 2.6. Serrations P4, type 14, others one 15, one 13. Cusps Mi, 
type 10:6, referred 11:6. Cusps M2, type and referred specimen 5:2. 
Crest of P4 elevated well above M^ 







'S© 



Figure 10.— Edypodus and Pared y pod u,s, comparative outline drawings of lower dentitions: a, E. grangerl 
Simpson, U.S.N.M. no. 9S01; 6, E. russeUi Simpson, U.S.N.M. no. 9765; c, E. sUbertingi Simpson, 
U.S.N.M. no. 9798; d, P. jepseni Simpson, U.S.N.M. no. 9769. Crown and external views, left lower 
jaws. Three times natural size. 

Remarks. — This species considerably resembles the preceding one, 
and I was at first inclined to consider its smaller size as due only to 
variatio», as it is well within the possible size limits. That would, 
however, make the range in Mi external cusp number for the com- 
bined species twice as great as has been demonstrated for any known 
species of this or allied genera, even in much larger samples, and the 
probability is very greatly against this occurring in a single species 
and against the association of larger cusp number with smaller size 
being due to accidents of sampling. It is possible also, although 
less clear, that association with a slightly larger length P4: length Mj 
ratio is significant. The added character of a more elevated P4 
makes the specific distinction practically certain. 

P4 of this species very closely resembles that of Edypodus coch- 
ranensis. However: (a) It here has a definitely larger notch for 
P3, (b) the localities are well separated, (c) the ages are distinctly 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



101 



different, (d) only P4 can be compared, and (e) extremely slight differ- 
ences in this tooth are commonly associated with specific or even 
generic differences in other parts of the dentition/" 

In size this species is a little closer to E. musculus than is E. grangeri, 
although still definitely larger, but its other distinctions from E. 
grangeri are distinctive in about the same degree from E. musculus. 

A tooth of this species (no. 6088) was referred by Gidley to "Ptilodus 
serratus" {—Halodon serratus Marsh) in his preliminary publication 
(1909, p. 622) but with the reservation that it might later be placed 
in a new species. Had he completed his work. Dr. Gidley would 
unquestionably have placed this specimen in a new species, as is done 
here. The remarks made above, regarding specimens of fPtilodus 
sinclairi referred tentatively to "Ptilodus formosus" are equally 
apropos here. 

Table 20. — Measurements of individual specimens of ?Ectypodus russelli 



U.S.N.M.no. 


LP4 


Ml 


Mj 


LPi 

LMi 


LMi 
WM, 


LM, 
LMi 


Serra- 
tions 
P^ 


Cusps 
M, 


Cusps 


L 


W 


L 


W 


Mj 


9766 - 


Mm 
4.9 
5.0 
5.1 


Mm 
2.9 
2.9 


Mm 
1.1 
1.2 


Mm 
1.6 
1.5 


Mm 
1.5 
1.4 


1.69 
1.72 


2.6 
2.4 


l.S 

i.y 


13 
14 

15 


11:6 
10:6 


5:2 


9765 .- 


5:2 


6088 



















7ECTYPODUS SI.LBERLINGI Simpson 

Figure 10, c 
f Edypodus silberlingi Simpson, 1935d, p. 226. 

Type. — U.S.N.M. no. 9798, left lower jaw with incisor and P4-M2. 
Collected by A. C. Silberling. 

Horizon and locality. — Gidley Quarry, Fort Union, Middle Paleocene 
horizon. Crazy Mountain Field, Mont. 

Diagnosis. — (Only one specimen.) Length P4, 3.3. Length Mi, 
2.3. Ratio length P4:length M„ 1.4. Length Miiwddth Mi, 2.6. 
Serrations P4, 12. Cusps Mi, 9-10:5-6."^ Crest of P4 relatively low. 

Remarks. — In most of its characters, this species falls weU within 
the range of fPtilodus sinclairi, with which it would be confused in 
casual examination, but its deviation from the mean of sinclairi in 
length of Ml is 5 times the standard deviation of the latter, and in 
the ratio length Mi '.width Mi, 2.3 times, and the marked difference 
in cusp number of Mi is also surely significant. The species cannot 
be, and the genera probably are not, the same. 

<' Russell (1929. p. 173) in describing E. cochranensis was doubtless referring to my IE. rusnlli when he 
wrote, "Undescribed premolars of about the same size as E. cochranensis occur in the Fort Union beds of 
Montana, but these teeth differ markedly from the present specimen in having a prouounced undercutting 
in the anterior margin of the crown." 

*» That is, clearly at least 9:5, and in each row rudiments of another cusp so that it is doubtful whether 
the count should be 9:5 or 10:6. 



102 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

Among other species, it most closely resembles Ectypodus musculus, 
but aside from the different horizon and locality it differs in being 
somewhat, perhaps significantly, smaller and in having more cusps 
on Ml, as well as other minor distinctions that may prove also to be 
significant when a larger sample permits their evaluation. 

Measurements of the type other than those given above: Width 
Ml, 0.9; length Mo, 1.2; width Ms, 1.0; ratio length Mi '.length Ms, 
1.9; cusps Ma, ?o:3. 

7ECTYPODUS species 

U.S.N.M. no. 9772 includes three unassociated last upper premolars, 
one broken, from the Gidley Quarry. They have one complete row 
of 11 cuspules, or serrations, and a rudimentary anteroexternal basal 
row of 2 cusps, both strong and distinct, the more posterior larger 
and opposite the third or fourth cusp of the main row. These teeth 
suggest Ectypodus musculus, but the elevation of the posterior end of 
the main crest is less than in that species, and the apex is not on the 
most posterior cuspule but on the fourth or fifth from the posterior 
end. Neoliotomus conventus is inadequately known, but apparently 
these specimens are less symmetrical in lateral contour. Size and 
cusp number surely distinguish the species from any comparable form, 
and the generic reference is doubtful. The lengths of the two more 
complete teeth are 4.8 and 4.5 mm. 

These probably represent the upper dentition of one of the species 
here named from lower jaws, and by inference somewhat more prob- 
ably one referred to ?Ectypodus, but the association cannot be estab- 
lished. From the ratio length P4: length P* in Ectypodus musculus 
(1.48), the lower P4 should be 6.7-7.1 mm in length, about as in 
fPtilodus douglassi, but the latter has no characters suggesting 
Ectypodus. fEctypodus grangeri may be based on the corresponding 
lower teeth, but it seems somewhat too small. 

Genus PARECTYPODUS Jepsen, 1930 

7PARECTYPODUS JEPSENI Simpson 
FiGXJRE 10, d 

? Par ectypodus jepseni Simpson, 1935d, p. 227. 

Tl/pe.— U.S.N.M. no. 9769, left lower jaw with P4-M1. Collected 
by A. C. Silberling. 

Horizon and locality. — Gidley Quarry, Fort Union No. 2, Crazy 
Mountain Field, Mont. 

Diagnosis. — (Only one specimen.) Length P4, 4.3. Length Mi, 
3.1. Ratio length P4: length Mi 1.4. Length Mi: width Mi, 2.2. 
Serrations P4, 11. Cusps Mj, 7:6. P4 long and low. No notch for P3. 

Remarks. — This can be compared only with the later Parectypodus 
simpsoni. Its longer Mi, lower length P4:length Mi ratio, smaller 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



103 



serration number, markedly different cusp formula of Mi, and other 
lesser differences show it to be markedly distinct. It differs even 
more, but in somewhat different ways, from Paredypodus tardus. 
The generic reference is very dubious. 

Measurements of the type other than those given above: Width 
Ml, 1.4. 

Genus EUCOSMODON Matthew and Granger, 1921 

EUCOSMODON SPARSUS." new species 

Figure II 

Type. — U.S.N.M. no. 10113, part of lower incisor, with a small 
adherent jaw fragment. Collected by A. C. Silberling. 

Horizon and locality. — Loc. 25, and referred specimens from Loc. 
51 and the Silberling Quarry, Fort Union, Middle Paleocene horizon, 
Crazy Mountain Field, Mont, 

Diagnosis. — Type incisor, maximum transverse diameter 4.0, mini- 
mum 1.4 mm, ratio 2.86. 




FiGURK \\.—Eucosmodon sparsus, new species, U.S.N.M. no. 10113: Part of lower incisor and fragment of 
jaw. External view and cross section at anterior end of incisor as preserved, with enamel band shown in 
heavier outline. Four times natural size. 

Remarks. — This is an interesting form worthy of formal record 
despite the imperfection of the material. Poor as this is, it fulfills 
the practical requirements of demonstrating distinction from any 
comparable species and ensuring that better specimens, when found, 
can be securely determined as of this species.^" The occurrence of 
three essentially similar specimens from three different localities and 
horizons, but all within this field and all in the No. 2 beds, covering 
a short span of time, also seems to demonstrate the validity and con- 
siderable range of the species. 

U.S.N.M. no. 9861 is a broken incisor from the Silberling Quarry 
and no. 9705 a similar specimen from Loc. 51. Their dimensions, 
given below, agree closely with those of the type. 

In maximum diameter these teeth approach E. americanus primus 
and are significantly smaller than other comparable species. In 
minimum diameter they are somewhat less and in compression ratio 

<' Sparsus, scattered, from the dispersion of the scantly known remains of the species. 
" Such specimens are almost surely included in the American Museum collection, but they are not yet 
prepared, and in any event it is proper that types be from the older collection, as far as possible. 

119212—37 8 



104 



BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



significantly more than E. a. 'primus. The minimum diameter is about 
that of E. teilhardi, but the maximum diameter and the compression 
are significantly less. E. americanus and E. molestus have the incisors 
significantly larger in both diameters and the compression less. Exact 
comparison with E. gratus Jepsen is not possible, but the incisor 
alveolus of that species measures 2.7 by 1.1 mm, ratio 2,45. The 
alveolus, and of course therefore the incisor as well, are much smaller 
than the incisor of E. sparsus. No known species aside from the 
several now mentioned could well be so closely related to E. sparsus 
as to demand differentiation. 

Table 21. — Comparison of data on lower incisors of Eucosmodon 



Species and specimen 



Diameters 



Maximum Minimum 



Ratio 



E. american us, type 

E. a. primus, paratype 

E. molestus, neotype 

E. teilhardi, paratype 

{Means 
10113 
9705 
9S6lII-l--III--I" 
{E. gratus, type, from alveolus) 



Mm 

6.0 

4. 2 

5. 8 
5. 2 
4. 3 
4. 
4. 1 
4.0 



(2.7) 



Mm 

2. 7 

1. 9 

2. 6 
1. 6 
1. 5 
1. 4 
1. 6 
1. 5 

(1. n 



2. 22 

2. 21 

2. 23 

3. 25 
2. 70 

2. S6 
2. 56 

2. 67 

(2. 45) 



The original of Douglass' plate 1, figures 18 and 20, probably belongs 
to this genus. If the scale of the figure is accurate (which is not 
invariably true in cases where I have studied Douglass' originals), the 
maximum diameter is about 3.7 mm, smaller than other specimens 
referred to this species, to which the specimen may nevertheless 
belong. 

Order INSECTIVORA Gray, 1827 

Forms that are at least nominally referable to the Insectivora con- 
stitute an important element in Paleocene and Eocene faunas, and 
this is particularly true in famias, like that here described, in which 
the microfauna is well or disproportionately represented. They are 
abundant in the present collection, including at least 10 species, all 
of which occur together in the Gidley Quarry. 

Despite diverse specializations, such as in the incisors of the Sori- 
coidea or the limbs of the Talpoidea, the recent insectivores are on 
the whole the most primitive of living placental mammals. The 
characters common to all of them, excluding the speciahzations of 
various particular phyla or larger groups, are in general those unques- 
tionably primitive for all placental mammals. The conception of 
the order and its definition thus do not so much depend on special 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 105 

characters developed within the order as on characters also basic 
for other orders but generally lost or more profoundly modified in 
those orders. Indeed the outstanding ordinal character of the 
Insectivora, paradoxically, is the absence of ordinal characters, in 
the sense that these are developed in other groups. 

Although the order is thus necessarily more loosely knit than is 
usual, it does not follow that it is altogether artificial. The retention 
of so many primitive characters is in itself some indication that this 
conservative group may have still been somewhat unified after the 
more progressive orders had acquired their distinctive characters. 
Furthermore, there are a few characters, such as those noted by 
Matthew in the astragalus, not of wholly generalized placental 
pattern and distinctive of the Insectivora as against many or most 
other mammals. There are also some characters, like the peculiar 
specializations of the incisors, that do not occur in all insectivores 
and are occasionally paralleled in other orders but that nevertheless 
appear so frequently among insectivores that they seem to reflect a 
certain genetic tendency and to help to bind the group together. 

Every individual living insectivore is a speciahzed animal, each 
species in its own way, and none can be considered, even structurally, 
as really representing the general placental ancestry in any very 
exact sense of the words. Yet the abstract conception Insectivora 
based on all known forms is such that it would, almost perforce, 
include the most primitive placental mammals. Probably the most 
remote ancestors (in the Cretaceous) of most, perhaps of all, the 
placental orders would be referable to the Insectivora by definition. 
In this sense the order Insectivora is prototjrpal and ancestral to all 
others among the Placentalia. 

Because the ordinal characters of the Insectivora are mainly primi- 
tive and because most of the Paleocene mammals are primitive, 
almost all known Paleocene forms resemble the Insectivora in many 
respects. If we knew the archaic mammals of the Paleocene but had 
no knowledge of any of the forms that lived between that time and 
the Recent, it would be a much more logical and practical system to 
refer almost all Paleocene mammals to the Insectivora," rather than 
to distribute them in numerous different orders as is now the usual 
practice. This distribution, in accordance with a "vertical" or so- 
called evolutionary conception of classification, is accomplished by 
the recognition of fossils intermediate between the Paleocene groups 
and the more distinctly separated later orders and of incipient speciali- 
zations within the Paleocene groups themselves that point toward 
groups later to become so distinct that they are granted ordinal rank. 

51 This is approximately the sense of Cope's Bunotheria, a broad group including the Insectivora and 
various other primitive mammals. Cope did, however, separate and distribute among other orders some 
Paleocene mammals, such as the Condylarthra, that were on the whole as primitive as those included in 
the Bunotheria. 



106 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

The concept Insectivora as it is applied to the Paleocene (and 
Eocene) faunas may thus inchide four different sorts of lesser groups: 

1. Very primitive placentals whose ancestral relationship to other 
later groups is not now recognizable. Naturally we do not know 
what groups may be included here, for the only way in which this 
situation could be shown to exist would be by recognition of the rela- 
tionships, but probably some so-called insectivores are of this char- 
acter. 

2. Animals that are in fact in or near the ancestry of later more 
specialized insectivores and that are therefore Insectivora sensu 
stricto. The Nyctitheriidae probably belong in this category, al- 
though the relationship is not definitely established. The other 
famiUes in the present fauna almost surely are not Insectivora in 
this special and most limited sense. 

3. Animals not structurally representative of the ancestry of later 
insectivores but sharing certain specializations with them that seem 
to indicate that they arose from a common stock with the later groups 
after the definite differentiation of that stock. These are also to be 
considered as Insectivora in a strict sense, even though the usage is 
broader than it is as apphed to the second category. The degrees of 
such collateral relationship vary greatly. Thus the Leptictidae fall 
definitely in this category, as they share many and apparently sig- 
nificant special characters with the Erinaceidae, although clearly not 
ancestral to that family. The Pantolestidae likewise show evidence 
of a special collateral relationship to the later insectivores, but the 
resemblance is less particular and the relationship evidently more 
remote. 

4. Groups that were derived from the nominally insectivore pro- 
toplacental stock but that had begun to diverge markedly from any 
other groups, without, however, having a sufficiently long history, 
being sufficiently important faunal elements, or acquiring sufficiently 
striking special characters to warrant the erection for them of a 
special order. Such groups are clearly Insectivora only in a very 
broad sense, yet their exclusion from the order would be a needless 
complication of taxonomy. The Mixodectidae appear to belong to 
this category. 

In this fauna there are 10 genera that are referable to the Insectivora 
in the general sense here accepted. Gelastops is evidently related to 
Didelphodus of the Lower Eocene and Acmeodon of the Middle 
Paleocene. It is perhaps a modified survivor of the protoplacental 
stock. Prodiacodon and Leptacodon are tj'^pical leptictids, Myrmeco- 
boides is an aberrant member of that group, and Bessoecetor is a primi- 
tive but typical pantolestid, while Aphronorus constitutes with the 
Torrejon Pentacodon a more aberrant group probably of pantolestid 
origin. Eudaemonema seems surely to be a mixodectid, although 



FORT UNIOX OF CRAZY MOUNTAIN FIELD, MONT. 107 

phyletically distinct from any other known genus. Picrodus is really 
of unknown affinities and is placed in the Insectivora only in default 
of other evidence. 

Family ?DELTATHERIDIIDAE Gregory and Simpson, 1926 
Subfamily Didelphodontinae Matthew, 1918 

Matthew placed this subfamily in the Leptictidae, pointing out 
that the affinities of Didelphodus are uncertain, but that it "can not 
easily be placed in any other family." Except for the general state- 
ment that "the teeth are in many respects not unlike those of the 
Leptictidae", he gave no definite reason for placing Didelphodus in 
that family, where it was decidedly anomalous. In defining the 
Deltatheridiidae, Gregory and Simpson (1926) stated that Didelphodus 
might belong in that group, and I still later (Simpson, 1928) gave in 
somewhat more detail the reasons for this tentative assignment. 

Gelastops of the present fauna is sufficiently close to Didelphodus 
to warrant their tentative collocation in one subfamily but, as brought 
out more fully in describing Gelastops, this is not certain. In any 
case Gelastops is poorly known and adds little to evidence for the 
affinities of this group. Its more aberrant premolar structure, still 
m.ore striking in the probably allied Acmeodon, does to some extent 
argue against close affinities with the much more primitive Cretaceous 
forms but this may merely indicate an incipient line of specialization 
within the Deltatheridiidae. The data do not warrant a more positive 
conclusion. On present evidence it seems well to retain Matthew's 
subfamily Didelphodontinae, for Didelphodus, Gelastops, Acmeodon, 
and probably Phenacops. This necessitates the proposal of a new 
subfamily Deltatheridiinae, defined, among other characters, by the 
less progressive premolars, less separated paracone and metacone, and 
narrower talonids. 

Genus GELASTOPS Simpson 

Gelastops Simpson, 1935d, p. 227. 
Emperodon Simpson, 1935d, p. 229. 

Type. — Gelastops parous Simpson. 

Type o/ Emperodon. — Emperodon acmeodontoides Simpson. 

Distribution. — Middle Paleocene, Fort Union, Mont. 

Diagnosis. — Canine large and erect. P4 intermediate in structure 
between Didelphodus and Acmeodon, with paraconid high on crown, 
metaconid nearly as high as protoconid and partly confluent with 
latter, a vertical crest descending posteriorly from the metaconid and 
another from the protoconid, and a small, bicuspid, basined talonid. 
Molars leptictid or didelphodontine, paraconids large and more inter- 
nal than in Prodiacodon or similar leptictids, trigonids elevated, that 



108 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

of Ml large relative to talonid and those of M2.3 compressed antero- 
posteriorly. M2 and particularly M3 reduced relative to Mi, heel of 
M3 much reduced but with projecting hypoconulid. 

Discussion. — By an unfortunate chance the National Museum 
material of this unusual genus does not include associated P4 and Mi. 
Since P4 seems clearly related to Acmeodon, while Mi seems just as 
clearly related to Didelphodus, and since the possibility of relationship 
between Acmeodon and Didelphodus had never been suggested, I was 
led to believe that two different animals were represented, one related 
to each of these genera. Specimens collected since this manuscript 
was first completed show that the P4 supposedly characteristic of 
Emperodon and the Mi supposedly characteristic of Gelastops really 
belonged to the same animal and this has made possible a last-minut« 
correction in the present work. 

There is little doubt that Gelastops is related to Acmeodon, although 
it is, on the whole, more primitive in structure. It had the anterior 
premolars less reduced than in the latter. P4 is superficially quite 
different in the two genera, but the differences appear to be modifica- 
tions of the same fundamental structure, wliich is unlike that of any 
other genera known to me. In Gelastops the paraconid is larger and 
more internal and the metaconid is distinct, but the latter is prob- 
ably represented in Acmeodon by the cuspule on the posterointernal 
crest descending from the protoconid, in which case the distinction is 
the relatively minor one that in Gelastops this cuspule is merely more 
emphasized and shifted slightly anteriorly. The peculiar protostylid 
is larger in Acmeodon but is also present in Gelastops. In Acmeodon 
the two crests run into the talonid rim and the valley between them 
into the talonid basin in such a way that the talonid is poorly differen- 
tiated, while in Gelastops the talonid is well set off by notches, but 
the parts seem to be entirely homologous in the two cases. The 
large and internal paraconid and talonid markedly narrower than 
trigonid, which so strikingly separate Acmeodon from the Leptictidae, 
are developed in almost exactly the same way in Gelastops. 

On the other hand, there is also good evidence for the relationship 
of Gelastops to Didelphodus. The general aspect of the jaw, canine, 
and cheek dentition is much the same in the two genera. In Gelas- 
tops Pi is probably more reduced and P2-4 more elevated. P4 is 
definitely more specialized m Gelastops than in Didelphodus, having a 
higher crown, more elevated (but little larger) paraconid, larger and 
much more elevated metaconid, and more prominent posterior crest 
on the metaconid. This crest is, however, distinctly present in 
Didelphodus and in general all the structural features seem to corre- 
spond in the two genera, the differences involving only relative 
proportions and prominence of the various parts. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 109 

The lower molars of Gelastops so closely resemble those of Didel- 
phodus as to make a hypothesis of relationship most reasonable. 
The only really clear difference is the greater elevation of the trigo- 
nids in Gelastops and this is not extreme. The upper molar men- 
tioned below also adds to the evidence, but the reference is not 
certain. 

Gelastops thus resembles both Acmeodon and Didelphodvs and is 
structurally almost intermediate between the two. Without pro- 
ducing absolute proof, it strongly suggests that the three genera 
Didelphodon, Gelastops, and Acmeodon belong to a natural group, 
and they are here tentatively recognized as constituting the sub- 
family Didelphodontinae. There are still difficulties in the way of 
this interpretation that perhaps can be resolved only by the discovery 
of upper dentitions of Gelastops and Acmeodon. The outstanding 
difficulty is that the series Didelphodus-Gelastops-Acmeodon is an 
excellent structural sequence in that order, on the basis of the parts 
now known in all, but that the most primitive genus, Didelphodvs, is 
the latest in time, a relationship that is fully possible but that re- 
quires better evidence for definitive acceptance. 

GELASTOPS PAROUS Simpson 

Figures 12, 13 

Gelastops parous Simpso?;, 1935d, p. 227. 
Emperodon acmeodontoides Simpson, 1935d, p. 229. 

Type. — U.S.N.M. no. 6148, right lower jaw with canine. Mi, M3, 
and alveoli. Collected by A. C. Silberling. 

Type of Emperodon acmeodontoides. — U.S.N.M. no. 9850, right 
lower jaw with P4, M2, and part of P3. Collected by A. C. Silberling. 

Horizon and locality.- — Type probably from Silberling Quarry,^^ 
other specimens from Gidley Quarry, Fort Union, Middle Paleocene 
horizon. Crazy Mountain Field, Mont. 

Diagnosis. — Sole known species of genus. Measurements in table 22. 

Remarks. — Besides the type and that of the synonym, there are 
two referred specimens from the Gidley Quarry in the National 
Museum collection: U.S.N.M. no. 9601, a right lower jaw with 
M2_3 and alveoli, and U.S.N.M. no. 9446, a right lower jaw with M2_3. 

From the alveoli it appears that a reduced Pi was present; this 
tooth is absent in Acmeodon and unreduced in Didelphodus. V2-3 
were present and each had two well-separated roots. The structure 
of P4 has already been sufficiently described except to note that the 
protoconid tip bends outward (labially) in a peculiar way, approach- 

" There is some inconsistency in the available records. It is certain that the type is from the Fort Union 
No. 2, and from its preservation it must be from one of these two quarries, but some error or omission had 
been made in recording the field number. Being collected in 1908, it is more likely to be from the Silberling 
Quarry. 



110 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

ing Acmeodon, its outer wall looking as if it had been plastically de- 
formed, by pressing the apex outward. Except for details in the 
generic diagnosis or evident from the measurements, the lower molars 
so closely resemble those of Didelphodus absarokae, described by 
Matthew (1918), that further description of them is not necessary. 

There is a s;ingle left M^, U.S.N.M. no. 9554, from the Gidley 
Quarry, that may belong to this species, although it differs more 
markedly from Didelphodus absarokae than do the lower molars. It 
is remarkably short and wide, or extremely transverse, and further 
differs from Didelphodus in the great extension of the parastyle spur, 
the slightly more external position of paracone and metacone, and the 
vestigial character of the metaconule. It resembles Didelphodus in 
other respects, such as the emarginate outer border, shelf-like meta- 



a 




Figure 12.— Oelastops parens Simpson, U.S.N.M. no. 
6148: Right lower jaw, external view. Twice natural 
size. 



Figure Vi.—Gelastops parens Simpson; 
a, Crown view of right lower teeth 
and alveoli, U.S.N.M. no. 9601; b, 
internal view of right lower jaw, U.S. 
N.M. no. 9850. Twice natural size. 



stylar extension, connate bases of paracone and metacone, and entire 
absence of hypocone or of anterior or posterior cingula. The trans- 
verse extension and the reduction of the metaconule are, furthermore, 
Didelphodus-like but here more extreme and the nonmarginal position 
of paracone and metacone are also Didelphodus-like but less pronounced. 



Table 22. — Measurements of individual specimens of Gelastops parous. 



U.S.N.M. no. 


P4 


M 1 


M J 


Ms 


M » 


L 


W 


L 


W 


L 


W 


L 


W 


L 


W 


6148 . 


Mm 


Mm 


Mm 
3.5 


Mm 
2.3 


Mm 


Mm 


Mm 
2.9 

2.7 

2.9 


Mm 
1.8 
1.9 

1.9 


Mm 


Mm 


9446 






2.5 
2.9 
3.0 


2.0 
2.2 
2.3 


2.7 




9850 


2.8 


1.9 








9601 








9554 .. . . 










5.0 























FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



Family LEPTICTIDAE Gill, 1872 



111 



Unlike many of the Paleocene and Lower Eocene groups referred 
to the Insectivora, the Leptictidae are Insectivora sensu strido. That 
is, they are not merely primitive forms that are presumed to have 
been derived from an undifferentiated insectivore stock and that do 
not enter well into an}^ other order, but are definitely insectivores in 
a special sense, clearly related to recent insectivores. Their affinities 
seem to be with the erinaceoids, although here they constitute an 
extinct side line, not ancestral to the true Erinaceidae. More exact 
elucidation of their affinities depends on full analysis of the characters 
of the Oligocene forms, which are known from nearly complete 
skeletons but have never been adequately studied. 

Matthew (1918) has pointed out that there is a group of genera 
undoubtedly leptictid (now about nine genera) and that in addition 
to these there are several diverse genera placed here without much 
positive evidence but in default of other indications. Didelphodus, 
Phenacops, and Acmeodon, then placed here by Matthew, are now 



Table 23.- 


-Compo 


rison of lou-er dentition of five genera of Paleocene Leptictidae 


Genus 


Canine 


P* 


Trigonids 


Molar paraconids 


M3 talonid 


Dlacodon 


Small.. 


With sharp, low, median 


Trigonids of P4- 


Lower than other 


Elongate. 






paraconid. Protocon- 


M3 moderate- 


trigonid cusps, 








id and metaconid op- 


ly elevated. 


small, submedi- 








posite and nearly 




an. 








equal. Heel basined, 












with 3 cusps, hypo- 












conid largest and near- 












ly confluent with hy- 












poconulid. 








Prodiacodon... 


Large.. 


With trigonid similar to 


Trigonids of P«- 


About as in Diaco- 


About as in 






Diacodon. Talonid 


M3 strongly 


don. 


Diacodon. 






with hypoconid rela- 


elevated. 










tively less dominant, 












hypoconulid more sep- 












arate, sometimes with 












4 distinct talonid cus- 












pules. 








Leptacodon 


Large.. 


Closely similar to Diaco- 
don, but metaconid 
smaller, usually pos- 
terointernal to proto- 
conid. Talonid small. 


Little elevated.. 


Nearly internal, 
otherwise more 
like Diacodon. 


Short. 


Myrmecoboxdes. 


Moder- 


Elongate, trigonid sim- 


Moderately ele- 


Small but nearly 


Very elon- 




ate. 


ilar to Diacodon. Tal- 
onid long, narrow, ba- 
sined, without dis- 
tinct hypoconulid, en- 
toconid about equal to 
hj'poconid. 


vated. 


as high as meta- 
conids, fully in- 
ternal, fusing 
with metacon- 
ids. 


gate. 


Xcnacodon 


Small.. 


With small basal para- 


do 


About intermedi- 


Short, strong- 






conid, large metaconid. 




ate between 


ly reduced. 






Talonid very short, 




Diacodon and 








not basined. 




Leptacodon. 





112 



BULLETIN 1G9, UNITED STATES NATIONAL MUSEUM 



tentatively removed to the Deltatheridiidae. The genus of most 
doubtful affinities still retained in this family is XenacodonMsitthew 
and Granger, of the Tiffany, 

The more positively leptictid genera Diacodon, Prodiacodon, 
Leptacodon, and Myrmecoboides also occur in the Paleocene, the last 
three being represented in this fauna. Table 23 shows some of the 
more striking distinctions in the lower dentitions of the five genera 
recorded from the Paleocene. 

Of these genera, Diacodon, Prodiacodon, and Lej)tacodon are typical 
leptictids and are evidently very closely allied, to such a point that 
they are rather difficult to distinguish. Myrmecoboides seems to be 
a true leptictid but is liighly distinctive and perhaps not closely 
related to any of the more typical genera. Xenacodon is a distinctive 
but poorly known and rather dubious form. 

Genus PRODIACODON Matthew, 1929 

PRODIACODON CONCORDIARCENSIS Simpson 

Figure 14 
Prodiacodon concordiarcensis Simpson, 1935d, p. 228. 

Type.— V.S.N. M. no. 9637, left lov/er jaw with P2, P4, M3, and 
alveoli. Collected by Dr. J. W. Gidley. 

Horizon and locality. — Gidley Quarry, Fort Union, Middle Paleocene 
horizon. Crazy Mountain Field, Mont. 




Figure li.— Prodiacodon concordiarcensis Simpson, U.S.N.M. no. 9637, left lower jaw: a, Crown view; 
6, internal view. Five times natural size. 

Diagnosis. — Much smaller than Prodiacodon puercensis. P4 v/ith 
paraconid more secant and projecting more anteriorly, talonid with 
three conical cusps, hypoconid largest and entoconid smallest. Mj 
with trigonid more slender and markedly elevated, talonid less 
elongate, with three subequal cusps. 

Remarks. — P2 has a high but small paraconid and low posterior 
cuspule. The horizontal ramus is ver}^ long and slender, and the 
anterior teeth were evidently procumbent. 



FORT UlSriOISr of crazy mountain field, MONT. 



113 



This delicate species differs so much from Prodiacodon puercensis 
that the generic reference is not at all certain, but the only alternative 
would be erecting a new genus, which is highly undesirable at present. 
The present form is apparently a typical leptictid, peculiar only in 
minute detaUs, and as close to Prodiacodon as to any other defined 
genus. It is almost equally close to Leptacodon, but its reference 
there would make the generic definitions almost unpossible to frame 
adequately. 

The type is the only known specimen. Its dimensions are as 
follows: Length P2, 1.3; width P., 0.5; length P^, 2.0; width P„ 1.1; 
length M3, 1.9; \v4dth M3, 1.2. 

Genus LEPTACODON Matthew and Granger, 1921 

LEPTACODON LADAE Simpson 

Figure 15 
Leptacodon ladae Simpson, 1935d, p. 228. 

r?/^e.— U.S.N.M. no. 9640, right lower jaw with P4-M3. Collected 
by A. C. Silberling. 

Horizon and locality. — Gidley Quarry, Fort Union, Middle Paleo- 
cene horizon, Crazy Mountain Field, Mont. 





Figure 1".. — Leptacodon ladae Simp- 
son, U.S.N.M. no. 9640, right 
lower jaw: a. Crown view; 6, in- 
ternal view. Five times natural 
size. 



Figure 16. — Leptacodon munuscu- 
lum Simpson, U.S.N.M. no. 
9819, left lower jaw: a, Crown 
view; 6, internal view. Five 
times natural size. 



Diagnosis. — Slightly larger than L. tener or L. packi and slightly 
smaller than L. siegfriedti, structurally closer to the former two 
species (subgenus Leptacodon) than to the latter (subgenus Leipsano- 
lestes). P4 elongate, paraconid median, metaconid very smaU but in 
the same poskion as in L. tener, talonid as in that species. Molar 
paraconids smaller than in L. tener but distinct and internal. Hypo- 
conulids of M1-3 more projecting than in L. tener. Talonid of M3 
more elongate and entoconid smaller. 

Remarks. — This species is referable to Leptacodon with very little 
doubt. Although fairly common in the Gidley Quarry, the speci- 
mens are all very fragmentary, and they add nothing to knowledge 
of the genus beyond making it a little more varied. 



114 



BULLETIN 169, UNITED STATES NATIONAL MUSEUM 



The dimensions of the type are as follows: Length P4, 1.4; width 
P4, 1.0; length M„ 1.5; width Mj, 1.2; length M2, 1.4; width M2, 1.3; 
length M3, 1.5; width M3, 1.1. 

The available numerical data on the whole sample are given in 
table 24. 

Table 24. — Numerical data on specimens of Leptaeodon ladae 



Variate 


N 


R 


M 


<r 


V 


LP4 

WP4 

LM, 

WMi 

LM2 

WM2 

LMa 

WM3 

LMi_3 


5 
5 

7 
6 
9 
8 
8 
7 
3 


1. 4-1. 6 

0. 8-1. 

1. 4-1. 6 
LO-1. 3 
1. 3-1. 6 

0. 9-1. 4 

1. 4-1. 6 
1. 0-1. 2 
4. 5-4. 7 


1. 48 

0. 90 

1. 53 ±0. 03 
1. 17 ±0. 04 
1. 43±0. 03 
1. 20 ±0. 05 
1. 51 ±0. 02 
1.09 ±0.02 
4.57 


0. 07 ±0. 02 
0. 09 ±0. 03 
0. 08 ±0. C2 
0. 14 ±0. 04 
0. 06 ±0. 02 
0.06 ±0.02 


4. 6±1. 2 
8. 1 ± 2. 3 

5. 7±1. 3 
11. 7±2. 9 

4. 0±1. 

5. 9±1. 6 



The two available specimens of L. tener are at or slightly below 
the observed lower limits for L. ladae in all molar dimensions. The 
deviations of the four available dimensions of the type of L. tener 
from the means of L. ladae, divided by the corresponding standard 
deviations of the latter (d/a) are as follows: 



LMi:-6.1 
WMi :- 5.0 



LM2:-4.0 
WM,:-2.9 



The size difference, slight as it is, thus appears to be significant. 
Individual measurements of L. packi are not available, but that 
species is very close to L. tener in size, hence probably also signifi- 
cantly smaller than L. ladae. 

LEPTACODON MUNUSCULUM Simpson 

Figure 16 

Leptaeodon munusculum Simpson, 1935d, p. 228. 

Type.— U.S. ISIM. no. 9819, left lower jaw with Mi and M3. Col- 
lected by A. C. Silberling. 

Horizon and locality. — Gidley Quarry, Fort Union, Middle Paleo- 
cene horizon, Crazy Mountain Field, Mont. 

Diagnosis. — Mj of about the same size as in L. tener, M3 more 
reduced. ^^ Paraconids smaller and more strictly internal. Talonid 
of M3 relatively narrower. 

Remarks. — This poorly known species is the smallest mammal in 
the collection and is one of the smallest mammals known. It is 



•3 The original diagnosis says "Slightly smaller than Leptaeodon tener", which was probably true of 
the dentition as a whole and perhaps of the animal, but Mi is as large as in L. tener. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT, 115 

almost certainly referable to this genus but is shown to be a dis- 
tinctive species even from the one very fragmentary specimen avail- 
able. Ml is 1.2 and M3 1.1 mm in length. The comparison with 
L. ladae by d/«T is thus as follows: 

LMi:4.7 LMa-.e.S 

The ratio LM1/LM3 compares as follows: 

L. tener (referred specimen) ".0.86. 

L. ladae (three specimens) : 1.00-1.07, mean 1.05. 

L. munusculuni: 1.09. 

M3 is thus more reduced in L. ladae and in L. munusculum than 
in L. tener. The difference between L. munusculum and L. ladae may 
be, but is not shown to be, significant. 

Genus MYRMECOBOIDES Gidley 

Myrmecoboides Gidley, 1915, p. 395. 

Type. — Myrmecoboides monianensis Gidley. 

Distribution. — Middle Paleocene, Fort Union, Montana. 

Diagnosis. — Canine of moderate size. Premolars well spaced. 
P4 elongate, with strong but low, median paraconid, metaconid well 
separated and nearly as high as protoconid, talonid long and narrow 
with small, subequal hypoconid and entoconid and hypoconulid 
barely suggested. Molars, particularly M3, -with, long talonids and 
with moderately elevated trigonids. Paraconids smaller than meta- 
conids but nearly as high and partly connate, so that paraconid and 
metaconid together form a twinned apex that is higher than the 
protoconid. 

Remarks. — Gidley stated that the name Myrmecoboides was "given 
to the ancient form on account of its likeness to Myrmecobius rather 
than as a positive assumption of real relationship." He did, however, 
state that the genus was marsupialian and probably related to the 
Myrmecobiidae, and he went into much detail regarding its bearing 
on marsupial evolution. Abel (1919) placed Myrmecoboides in the 
Myrmecobiidae. Osgood (1921) stated that Myrmecoboides might 
well be ancestral to Caenolestes, if it was a marsupial. Sclilosser (1923) 
classified it in the Myrmecobiidae but noted that it might not be mar- 
supial. Longman (1924) gave a resume of Gidley's view, stating (as 
had Gidley) that the resemblances to Myrmecobius were suggestive 
but not conclusive. Matthev/ (1916) had, however, quickly pointed 
out that the characters of Myrmecoboides are not myrmecoboid or 
marsupial, but leptictid and placental. Gidley also came to accept 
this conclusion (personal communication) but apparently did not 
publish this fact. Students of Paleocene mammals have long realized 
that Myrmecoboides cannot be a marsupial, but aside from Matthew's 
brief statement, which has been overlooked by almost all later com- 



116 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

mentators, the evidence has not been clearly stated in publication and 
Gidley's abandoned view is becoming entrenched in the literature. 
It is therefore necessary to consider it here. 

Gidley did not explicitlj^ discuss the evidence for referring Myrmeco- 
boides to the Marsupialia. It is clear that the reference was based 
almost entirely on the molariform character of the fourth cheek tooth, 
and in part simply on a general resemblance to the one marsupial genus 
Myrmecohius. Gidley mentions the three possibilities regarding the 
molariform tooth: that it is a true molar, that it is a deciduous molar, 
and that it is a true premolar. He cites the narrower crown, smaller 
talonid, and large, anteriorly directed paraconid as seemingly preclud- 
ing the possibility that the tooth is a true molar. This evidence is 
valid, and to it may be added (as first pointed out by Matthew) the fact 
that the protrusion and wear of the tooth definitely prove that it was 
erupted long after the following tooth, which could not be true of a 
first molar. Gidley states that the very complex structure in com- 
parison with P3 opposes the supposition that this is P4 and supports 
his conclusion that it is dm4, retained in the adult dentition. But the 
relative time of eruption, as first shown by Matthew, is impossible for 
dm4, which in all known mammals is erupted before Mi rather than 
long after, as the tooth in question is in Myrmecoboides. Further- 
more, the fourth cheek tooth in marsupials, whether it be Mi or dm4, is 
erupted before the following tooth or at almost the same time. Gidley 
also seems to have overlooked, momentarily, the fact well known to 
him that in the Leptictidae and some other unquestionable placentals 
P4 is characteristically as molariform as this tooth, or more so, even 
though P3 may be as simple as in Alyrmecoboides. It may be con- 
cluded, and Gidley also did conclude on more mature deliberation, 
that this is certainly P4, and hence that its evidence is entirely opposed 
to marsupial and in favor of placental affinities for the genus. 

Gidley analyzed all the resemblances to and differences from 
Myrmecobius. The only resemblances that could be supposed to 
carry much weight are the spacing of the premolars and the elevation 
of the internal cusps of the molars. These characters also do occur in 
placentals and are highly aberrant among marsupials. These, and all 
the other lesser points of resemblance, would perhaps tend to link 
Myrmecoboides to Myrmecobius if the former were otherwise proved to 
be a marsupial, but they have no value as to the primary question of 
showing it to be marsupial. There are indeed profound differences 
between the fossil and Myrmecobius. Gidley recognized these but con- 
cluded that degeneration could lead to this great transformation, which 
is true but is not evidence that it did so. On the other hand, Myrmeco- 
boides has the basic and diagnostic characters of the Leptictidae, and the 
Myrmecobius-\\]s.e characters can only be interpreted as superficial, aber- 
rant, habitus characters bringing about a slight degree of convergence. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 117 

The fact that Myrmecohoides is not a marsupial obviously deprives 
it of any bearing on whether the fourth cheek tooth of marsupials is 
dm4 or Ml, a question that Gidley properly discussed when under a 
misapprehension as to the affinities of the genus. It also removes this 
much support from Gidley's thesis, which was, however, also sup- 
ported by other evidence, that the Australian families were differen- 
tiated outside Australia and at a very early date.^* 

Among the Leptictidae, Myrmecohoides is aberrant and does not 
belong with such typical genera as Diacodon or Leptacodon, although 
its less direct relationship with them is highly probable. 

MYRMECOBOIDES MONTANENSIS Gidley 

Figures 17, 18 
Myrmecoboides montanensis Gidley, 1915, p. 395. 

Type. — U.S.N. M. no. 8037, left lower jaw with canine and P1-M3. 
Collected by A. C. Silberling. 

Horizon and locality. — Gidley Quarry, Fort Union, Middle Paleo- 
cene horizon, Crazy Mountain Field, Mont. 

Diagnosis. — Sole known species of genus. Dimensions below. 

Remarks. — Gidley (1915) has accurately described the lower denti- 
tion, and the slightl}^ different emphasis demanded by transfer to this 
family is supplied by the revised generic diagnosis. The second spec- 
imen mentioned by Gidley is U.S.N.M. no. 9418, which has only Mi.2 
and these so worn that the cusp structure cannot be made out. 

U.S.N.M. no. 9552 is a right upper jaw with P'^-M^ that is so well 
suited to be the upper dentition of Myrmecoboides montanensis, and 
not of any other knowTi species in the fauna, that it may be referred 
here. Dr. Gidley has noted that this is probably the upper dentition 
of Myrmecoboides — further evidence of his later recognition of the 
affinities of the genus, for this upper jaw is entirely leptictid in char- 
acter and does not at all resemble Myrmecobius. These upper teeth 
are very close to those of Prodiacodon throughout. P* seems to have 
had the paracone and metacone better separated in Mrjrmecohoides, 
but is imperfect in this region. M^ has the external shelf more pro- 
nounced, the parastylar and metastylar lobes more projecting, a deep 

" When Gidley wrote, it was a reasonable a priori assumption that diverse marsupials would be the micro- 
faunal elements most likely to appear in the Paleocene, although subsequent discovery has shown this not 
to be the case. He was inevitably predisposed toward this view (as was also Matthew and as were other con- 
temporaneous students), and his preliminary note on Myrmecoboides suffered from this preconception. It 
is further exemplified by his manuscript notes on severa 1 other placental genera labeled as "Marsupial No. 1" 
and so on; it has not seemed necessary to cite this first impression in each case, as Dr. Gidley would certainly 
have abandoned it before completing his studies. Dr. Gidley also had a strong and more personal predis- 
position, strikingly exemplified in the Myrmecoboides paper, to believe that the modern mammalian famDies 
were of extremely remote origin. This is a legitimate thesis, and the erroneous nature of part of the supposed 
evidence does not remove the possibility or vitiate Gidley's whole argument. His conclusion unquestion- 
ably contains an important truth, but I believe, apparently with the consensus of recent students, that he 
overemphasized its importance and extent. 



118 



BULLETIN 16 9, UXITED STATES NATIONAL MUSEUM 




Figure l' .—Myrmecoboides montanensis Oidley, U.S.N.M. no. 8037, left lower jaw: a, Crown view; 6, in- 
ternal view. Four times natural size. 




Figure 18.— Mi/rmecoboides montanensis Gidley, U.S.N.M. no. 9o52, right upper P'-M^, crown view. Four 

times natural size. 

median notch in the external border, and the hypocone more internaL 
]\P has the outer portion analogously modified, but this is less dis- 
tinctive from Prodiacodon than is M^ M^ is of almost identical struc- 
ture in the two genera. 

Table 25. — Measurements {in mm) of the type and of the referred upper jaw of 
Myrmecoboides montanensis 



Pi 


P2 


P3 


P4 


M, 


M2 


Ms 


P< 


Ml 


M2 


M3 


L 


W 
0.6 


L 

1.8 


W 
0.8 


L 
2.3 


W 


L 


W 


L 


W 


L 


W 


L 


W L 


W 


L 


W 


L 


W 


L 


W 


1.1 


0.9 


2.7 


1.3 


2.4 


1.5 


2.3 


1.5 


2. f) 


1.5 


2.6 


3.3 


2.3 


3.7 


2.4 


3.8 


2.0 


3.7 



Family NYCTITHERIIDAE Simpson, 1928 

This family was established to include a number of rather poorly 
known Paleocene and Eocene genera, all represented by species of 
small or minute size, that probably represent a single varied group 
and that seem to be primitive shrewlike insectivores, without any of 
the specializations characteristic of the true shrews. In this respect 
the dentition is molelike rather than shrewlike, but there is no evi- 
dence of definitely talpid specializations. As Matthew (1909) has 
pointed out (in other words), speaking of Eocene genera that I have 
since placed in this family, they seem to combine all the most primi- 
tive characters of the moles and the shrews. To this extent the evi- 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 119 

dence suggests an undifferentiated group from which these late insec- 
tivores arose, but annectant types are lacking and knowledge is too 
incomplete to test this hypothesis adequately. Matthew (1918) has 
also pointed out that Nyctitherium itself may be a chiropteran, and 
this may be true of the whole group, or it may be a primitive complex 
allied or ancestral to all three groups, Talpoidea, Soricoidea, and Cliir- 
optera, although there is reason to suppose that these three groups 
were already distinct before the end of the Paleocene. It is likewise 
possible that two or all three of these groups had acquired their skel- 
etal specializations but not their dental characters in the Paleocene 
and that the nyctitheriids are an artificial assemblage based on dental 
resemblance only. Despite this possibility, it seems most practical to 
continue to associate them in this family until some broader basis for 
classification becomes available. 




Figure 10.— Stilpnodon sjmplkidens Simpson, U.S.N.M. no 9629, left lower jaw: a, Crown view; 6, internal 

view. Five times natural size. 

In the National Museum collection only one nyctitheriid specimen 
is available, but it represents a distinctive genus, Stilpnodon. It 
is not very close to any other known genus, and its reference to the 
family is not certainly established, but it is most conveniently placed 
here. It shares with Leptacodon munusculum the distinction of being 
the smallest known mammal of this fauna. 

Genus STILPNODON Simpson 

Stilpnodon Simpson, 1935d, p. 229. 

Type. — Stilpnodon simplicidens Simpson. 

Distribution. — Middle Paleocene, Fort Union, Mont. 

Diagnosis. — P4 with very high, slender main cusp, minute rudimen- 
tary anterior basal caspule, no metaconid, simple nonbasined talonid 
with one cuspule. M3 reduced, with distinct, low, nearly median 
paraconid, trigonid erect and moderately elevated above talonid, 
protoconid large, trigonid nearly as long as talonid, talonid short and 
much narrower than trigonid. 

119212—37 9 



120 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

STILPNODON SIMPLICIDENS Simpson 

Figure 19 
Slilpnodon simplicidens Simpson, 1935d, p. 229. 

Type.— U.S. ISiM. no. 9629, left lower jaw with P3_4, M3, and 
alveoli. 

Horizon and locality. — Gidley Quarry, Fort Union, Middle Paleo- 
cene horizon. Crazy Mountain Field, Mont. 

Diagnosis. — Sole known species of genus. P4 length, 1.0 mm. M3 
length, 1.2 mm. 

Remarks. — P3 is very simple, without anterior basal cuspule and 
with the sloping heel not forming a distinct cusp. From its roots, 
P2 was of about the same size as P3. The posterior mental foramen 
is beneath the anterior root of P4. 

Family PANTOLESTIDAE Cope, 1884 

In his Bridger memoir Matthew (1909) united various genera pre- 
viously widely scattered in the system and placed them in the Pantoles- 
tidae. From a study of Pantolestes, a relatively specialized but well- 
knowQ Middle Eocene genus, he showed that at least the typical 
members of the family have basic insectivore characters, overlain by 
peculiar specializations not closely paralleled in recent insectivores. 
He interpreted the majority of these specializations in Pantolestes as 
adaptations to aquatic, or to amphibious, life. At that time he pointed 
out that Palaeosinopa, then laiown from the Lower Eocene, is closely 
related to Pantolestes and that Pentacodon, of the Middle Paleocene, 
might tentatively be placed in this family. In 1918 Matthew revised 
and carefully described the Lower Eocene Palaeosinopa, again 
emphasizing its close relationship to Pantolestes, and reviewed the 
evidence for reference of these genera to the Insectivora. This 
evidence, which still appears to be adequate for such a conclusion is, 
in briefest possible outline, that the pantolestid dentition is, indeed, 
more creodontlike than like any recent insectivore but is also closely 
similar to the unquestionably insectivore leptictids, and that numerous 
characters of skull and skeleton (especially the astragalus) are quite 
unlike any known creodonts or other carnivores but do resemble the 
Leptictidae and other Insectivora. A special point of the evidence 
(singled out by Sclilosser, see Matthew, 1918, for undue emphasis) 
is the position of the posterior mental foramen beneath Mi, a character 
known only in Insectivora, although not characterizing all members 
of that order. 

Various fragments suggested the presence of this family in the 
Upper Paleocene (e. g., Simpson, 1927), and Jepsen (1930a) referred a 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 121 

partial jaw from the Aliddle Paleocene to Palaeosinopa. 1 have 
described a genus, Bessoeceter, from the Upper Paleocene (Simpson, 
1936b). The present fauna includes a distinctive species that seems 
surely to be closely allied to or in the Palaeosinopa-Pantolestes line 
and is tentatively referred to Bessoecetor, thus definitely projecting 
the typical pantolestid phylum back into the Middle Paleocene. It 
also includes in Ajphronorus an ally of Pentacodon, represented by 
much better material than is that Torre j on genus and much improving 
our knowledge of this small group. 

The probable relationship of Pentacodon and Ajphronorus, on one 
hand, and Bessoecetor, Palaeosinopa, and Pantolestes, on the other, is 
confirmed and strengthened by the present evidence. In both the 
lower jaw has a large semiprocumbent canine followed by three small 
elongate premolars of similar pattern in the two groups and then by 
a relatively enlarged premolar, the pattern of which is, however, 
unlike in the two lines. The molars, upper and lower, are of almost 
exactlj^ similar pattern, with only such minute differences as are 
encountered among veiy closel}- allied genera. The posterior mental 
foramen is beneath Mi in both cases and the other known osteological 
characters, although few and not veiy distinctive, are generally 
similar. 

The only characters opposing such relationships are those of P^4, 
which are more and differently specialized in Pentacodon and Aph- 
ronorus than in Bessoecetor or even the much later genus Pantolestes. 
These marked differences do not seem to exclude a family relation- 
ship, but they do show that two divergent and sharply defined groups 
are included, especially when the distribution of the various genera is 
taken into account. In the present state of knowledge it seems 
convenient to formalize this distinction by placing the known genera 
in two subfamilies, the Pantolestinae with Bessoecetor, Pantolestes, 
Palaeosinopa, and perhaps some less well known forms, and the 
Pentacodontinae with Pentacodon and Aphronorus. For the present 
these are immediately and adequately distinguishable from the 
characters of P*4 as given in the diagnosis below. 

Pantolestinae, new subfamily 

Type. — Pantolestes Cope, 1872. 

Distribution. — Middle Paleocene to Middle Eocene, North America. 
Lower Eocene, Europe. 

Diagnosis. — P*4 relatively little enlarged. P4 compressed, no 
metaconid, semishearing, heel essentially unicuspid and little or not 
basined. P^ with compressed amphicone, no metacone, low, sharp 
styles, small protocone without cingula. 



122 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

Genus BESSOECETOR Simpson 

Bessoecetor Simpson, 1936b, p. 9. 

Type. — Bessoecetor thomsoni Simpson. 

Distribution. — Middle and Upper Paleocene, Fort Union, Montana. 

This genus was based on an unusually good suite of specimens from 
the Scarritt Quarry. It is evidently very closely allied to Palaeosinopa 
but seems to be slightly more primitive in several respects. The 
species Palaeosinopa diluculi, previously recorded from the present 
fauna (Simpson, 1935d, p. 230) appears to be more nearly related to 
Bessoecetor and may be provisionally placed in that genus, although it 
is too poorly known to reveal all the desired generic characters. Most 
of the characters in which it differs from Lower Eocene species of Pal- 
aeosinopa and which were therefore given as specific characters in the 
original diagnosis are now shown by the fine material of Bessoecetor 




Figure 20.— Bessoecetor diluculi (Simpson), U.S.N.M. no. 9810, with parts in outline added from U.S.N.M. 
nos. 9312 and 9539, left lower jaw: a. Crown view; 6, internal view. Three times natural size. 

thomsoni to be generic characters of Bessoecetor. Tliis includes, most 
notably, the strongly trenchant P4 with large anterior basal cusp and 
incipient basining of talonid, the relatively small expansion of the 
hypocone shelves, and the less reduced M^. The Middle Paleocene 
form also has the sharply distinguished molar talonid cusps character- 
istic of Bessoecetor. 

BESSOECETOR DILUCULI (Simpson) 

Figures 20, 21 
Palaeosinopa diluculi Simpson, 1935d, p. 230. 

Type.— U.S.N.M. no. 9810, left lower jaw with P4-M2. Collected 
by A. C. Silberling. 

Paratype. — U.S.N.M. no. 9553, left upper jaw with P^'-M^ (some- 
what broken). Collected by A. C. Silberling. 

Horizon and locality. — Gidley and Silberling Quarries, Fort Union, 
Middle Paleocene horizon, Crazy Alountain Field, Mont. 



FORT U:N^IO]Sr OF CRAZY LIOUNTAIN FIELD, MONT. 



123 



Diagnosis. — P4 and M2-3 significantly larger than in B. thomsoni, Mi 
about same size. Heel of P4 relatively larger, talonid of M3 more 
elongate. Amphicone of P* more compressed. 

Remarks. — The dentition is closely similar to that of B. thomsoni, 
fully described elsewhere (Simpson, 1936b). 

Table 26. — Dentition measurements (in mm) of Bessoecetor diluculi 



U.S.N.M.no. 


Vt 


M, 


Ms 


M, 


L 


w 


L 


w 


L 


w 


L 


w 


9810 




1.3 


2.4 


1.7 


2. 5 
2. 6 
2.7 


2.0 
2. 2 
2.0 


3.3 




9312 




2 3 


9442 




1. 4 
1.3 


2.3 

2.7 


1. 7 
1.8 




9539 


3. 2 




U.S.N.M. no. 


P* 


Ml 


MJ 


MJ 




L 


w 


L 


w 


L 


W 


L 


w 


9553 






2. 7 
2.5 


3.4 


2.8 
2.6 


3. 8 
3.5 


2.0 




9585 


2.6 




3. 5 








Figure 21.— Bessoecetor 
dilaculi (Simpson), U.S. 
N.M. no. 9553, with part 
in outline added from 
U.S.N.M. no. 9585, left 
upper jaw: a, External 
view; 6, crown view. 
Three times natural size. 





Figure 22.— Aphronorus fraudator Simpson, U.S. 
N.M. no. 6177, left lower jaw: a. Crown view; 6, 
external view. Three times natural size. 



Pentacodontinae, new subfamily 

Type. — Pentacodon Scott, 1892. 

Distribution. — Middle Paleocene (and doubtfully Upper Paleocene), 
North America. 

Diagnosis. — P^ much enlarged. P4 with very heavy protoconid, 
sloping backward, well-developed metaconid, and basined heel. P* 
with massive, conical, paracone, smaller but sharply distinct metacone, 



124 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

styles small or lacking, and large, low protocone with widely expanded 
anterior and posterior cingula. 

Remarks. — Aside from its probable relationship to the Pantolestinae, 
this group shows some resemblance to the Anisonchinae and to the 
Apheliscidae, but in neither case is this resemblance close enough to 
suggest real ajQanity. The enlargement of P^ and the general but 
primitive stamp of the molars is not unlike the Anisonchinae but 
does not include any detail such as might indicate a real relationship. 
P*4 still more resemble those of Apheliscus but differ in cusp structure, 
and the molars are widely different. It is not impossible that Aphelis- 
cus is an offshoot of the same stock, but real evidence for such a hypoth- 
esis is lacking. 

Genus APHRONORUS Simpson 

Aphronorus Simpson, 1935d, p. 230. 

Type. — Aphronorus fraudator Simpson. 

Distribution. — Middle Paleocene, Fort Union, Montana. 

Diagnosis. — Generally similar to Pentacodon. P4 with anterior end 
less produced downward than in Pentacodon, talonid more distinctly 
basined, with second cuspule more distinct. M2_3 less reduced 
relatively to Mi. Trigonids of Mi_2 relatively shorter and entoconids 
relatively higher than in Pentacodon. Three talonid cusps of M3 
more distinct. P* with metacone well differentiated, protoconiile 
distinct. M' and to less degree M^ slenderer and more transverse 
than in Pentacodon, more leptictid in aspect. 

Remarks. — This genus is evidently closely allied to Pentacodon, and 
its distinctive characters, taken together, do not definitely suggest 
that it is necessarily either an earlier or a later stage in the Pentacodon 
phylum. Evolution could have proceeded in either direction, or the 
two may have diverged from a common ancestry. Nevertheless 
Aphronorus does seem to resemble Palaeosinopa in more details than 
does Pentacodon and to this extent may be supposed to retain more of 
of the primitive characters of the family as a whole, despite its possible 
divergence in other respects. 

APHRONORUS FRAUDATOR Simpson 

Figures 22-24 
Aphronorus fraudator Simpson, 1935d, p. 230. 

T?/2?e.— U.S.N.M. no. 6177, left lower jaw with P4-M3. Collected 
by A. C. Silberling. 

Horizon and locality. — Gidley and Silberling Quarries, Fort Union, 
Middle Paleocene horizon. Crazy Mountain Field, Mont. 

Diagnosis. — Sole known species of genus. Dimensions given in 
table 27. 

Remarks. — The lower canine, known from its alveolus only, is large 
and semiprocumbent. Pi is very small and appears to have a single 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



125 



root. P2 is likewise small but more elongate and with two roots. The 
only specimen that shows Pi_2 is senile and these teeth are truncated 
by wear at the bases of the crowns. P3 is larger than P2 but also 
small in relation to the whole dentition. When unworn it has a 
triangular protoconid followed by a heel with a slight interna"! basin 
and two rudimentary posterior cusps. P4 is much enlarged and has a 
massive protoconid, which slopes backward, and a lower distinct 
metaconid, closely applied to the posterointernal base of the protoco- 




FiGURE 23.— AphronormfraudatoT Simpson, U.S.N.M. no. 9448, with parts in outline added from U.S.N.M. 
DOS. 9291 and 9519, right lower jaw: a, Crown view; 6, internal view. Four times natural size. 




Figure 2i.—Aphro7iorusfraudator Simpson, U.S.N.M. no. 9560, with tooth in outline added from U.S.N.M. 
no. 9565, left upper jaw: a. External view; 6, crown view. Four times natural size. 

nid. Anterior to this there is a sharp internal cingulum, turning into 
a vertical crest at the anterior midline of the tooth, but there is usually 
no paraconid or anterior cuspule, although in one or two specmiens 
there is a slight tendency to develop a cuspule here. The large heel 
has its main cusp external to the midline, connected by a sharp crest 
to the middle of the trigonid base. Internal to this crest is a basin, and 
a second, smaller and less distinct cusp is near the posterointernal 
corner of the tooth. 



126 



BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



Tlie lower molars decrease in size from Mi to M3. The paraconids 
are small and tend to assume a conical shape but are still connected to 
the anterior protoconid crest. The paraconids are slightly internal 
to the midline. Metaconids and protoconids are nearly equal. The 
talonid is wider than the trigonid on Mi, about equal on M2, and 
narrower on M3. On M1.3 the tliree talonid cusps are about equal in 
height but the hypoconulid is smallest. On M3 the hypoconulid is 
enlarged and projects posteriorly in the usual manner. 

The mandible is lighter than in Pentacodon and very closely ap- 
proaches Palaeosinopa in all respects. 

P^ is 3-rooted and has a single outer cusp like that of P* on a smaller 
scale save for the absence of a metacone. The protocone is small, and 
there are no cingula. P^ is a pecuhar, large, heavy tooth. Its con- 
tour is hourglass-shaped, with median constriction and expanded 
equal inner and outer lobes. The paracone is nearly circular in sec- 
tion and is heavy and tall and slopes slightly backward, like the pro- 
toconid of P4. It is followed by a smaller metacone. There is only 
the vaguest rudiment of a parastyle, but a very small metastyle is 
present. The protocone is crescentic and large but lower than the 
paracone. There is a small protoconule and rudimentary metaconule. 
Approximately equal and expanded anterior and posterior cingula 
occur on the protocone base, and each tends to develop into a cuspule 
(protostyle and hypocone). The upper molars are of leptictid type, 
strongly transverse, with emarginate external shelves, projecting 
parastylar and metastylar lobes (especially on M^), metacones sHghtly 
smaller than paracones, conules distinct, anterointernal cingula, and 
low hypocones slightly more internal than the protocones. M^ is 
reduced in the usual manner, with metastyle and hypocone absent and 
metacone small. 

Table 27. — Numerical data on Aphronorus fraudator 



Variate 


N 


R 


M 


tr 


V 


LP4 


10 

10 

10 

10 

12 

11 

7 

7 

8 

8 

8 

7 

4 

3 

2 

2 


3. 2-3. 8 
2. 0-2. 4 
2. 8-3. 1 

1. 8-2. 4 

2. 5-2. 9 

1. 9-2. 4 

2. 6-2. 9 

1. 7-2. 1 

2. 5-3. 1 

3. 5-4. 3 

2. 5-2. 8 

3. 6-3. 9 

2. 2-2. 6 

3. 9-4. 1 
1. 5-1. 9 
3. 3-3. 6 


3. 52 ±0. 05 
2. 15 ±0.05 
2. 88±0. 03 
2. 18 ±0.05 
2. 67 ±0.04 
2. 17 ±0. 03 
2. 79 ±0.04 

1. 90 ±0. 05 

2. 84 ±0. 06 

3. 88 ±0. 08 

2. 68 ±0.03 

3. 80 ±0. 04 
2.43 

4.00 
1.70 
3.45 


0. 17 ±0.04 
0. 14 ±0. 03 
0. 098±0. 022 
0. 17 ±0.04 
0. 13 ±0.03 
0. 114 ±0.024 
0. 10 ±0. 03 
0. 12 ±0. 03 
0. 18 ±0. 05 
0. 22 ±0. 05 
0. 097±0. 024 
0. 11 ±0. 03 


4. 9±L 1 


WP4 _ 


6. 7 ± 1. 5 


LMi 


3. 4 ± 0. 8 


WM, 

LM2 


7. 6±L7 
4. 7 ± 1. 


WM2 

LM3- 


5. 2±1, 1 
3. 5 ± 0. 9 


WM3 

LP< 


6. 3±1. 7 
6. 3 ± 1. 6 


WP^ 


5. 6 ± 1. 4 


LMi 


3. 6±0. 9 


WM» 

LM2 


2. 8±0. 8 


WM2 _. 

LM» 




WM3 





rORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 127 

Family MIXODECTIDAE Cope, 1883 

Previous views as to the affinities of tliis peculiar group have been 
summed up by Matthew (1909, 1915, and Pale. Mem.). In briefer 
resume, Cope considered the mixodectids as primates. Matthew 
(1897) concurred formally but suggested that Mixodectes itself might 
rather be a rodent. Osborn (1902) accepted and expanded this view, 
defining for the mixodectids a rodent suborder Proglires. Wortman 
(1903) argued for their return to the Primates, Finally, Matthew 
(1909 and subsequently) concluded that they probably belong in the 
Insectivora. 

Two very distinctive genera, Evdaemonema and Elpidophorus, have 
recently been added to the family. They add to the known variety 
and have an interesting bearing on relationsliips within the family, as 
brought out below, but they do not much alter the evidence for ordinal 
relationships. 

Skeletal remains referred to Indrodon by Osborn and Earle and to 
Microsyops by Wortman, in each case considered as indicating primate 
affinities, have been shown (Matthew, 1909) to be doubtfully or not 
associated. An astragalus and other fragments referred to Mixodectes 
were at first said by Matthew (1897) to be rodentlike and later (1909) 
to be equally insectivorehke and in any case not similar to any known 
primate. 

The dentition is said, even by Matthew in rejecting primate affini- 
ties, to be primatehke. There is, indeed, some resemblance to various 
primate genera in a few details, for instance the upper molars suggest 
Shoshonius in general proportions and in the strong mesostyle, and 
the enlargement of one anterior tooth and development of a diastema 
by loss of other teeth are also seen in Tetonius and some other genera. 
Such resemblances seem to have no value in the determination of 
affinities, since they refer to single characters of various different 
primates that are, in just these characters, highly aberrant among the 
primates as whole. Aside from such points, which can almost be 
discarded categorically as more likely to be convergent than not, I 
detect no primate resemblances in the teeth that go beyond the general 
Paleocene tuberculosectional pattern common to many different 
orders at this time. As set forth in the section of this paper dealing 
with the Primates, the Paleocene and Eocene primates, despite their 
primitive character, do have a distinctive stamp in molar pattern that 
is common to all of them and that is not seen to occur in any other 
order. The mixodectids do not have any of these truly distinctive 
and (at this time) ordinal primate characters. On the contrary, their 
high sharp cusps (notably in the talonids), elevated trigonids and 
internal lower cusps, displaced hypoconulids, and many other dis- 
tinctive details are quite unkno^\Ti among any primates and some of 



128 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

their family characters, such as the ectoloph construction, are ap- 
proached only as decidedly aberrant generic characters by one or a few 
primate genera. 

If we grant Matthew's second opinion that the astragalus of Mixo- 
dectes does not have diagnostic ordinal rodent characters, the evidence 
for rodent relationships is little more than the presence of enlarged in- 
cisors and (in some but not all genera) of more or less molariform pre- 
molars. Both these characters also appear independently in insecti- 
vores, numerous different lines of ungulates, primates, marsupials, 
and other orders. Nor are they really rodentlike in precise detail in 
this group. Indeed, there now seems to be no actual evidence that 
the mixodectids are related to rodents. 

Granting the usage of Insectivora not only to include the recent 
groups but also numerous extinct forms that necessitate definition on 
primitive characters only, we may well caU the mixodectids insecti- 
vores. Negatively, it may be said that no other defined order could 
receive them, and positively that their dentition is insectivorelike at 
least in habitus, that the astragalus is more like that distinctive of 
insectivores than like any other group except rodents (which are 
excluded by the dentition), and that in general they have the primitive 
features by wliich the Insectivora sensu lato are defined. 

It is probable that the mixodectids include a related group of phyla 
that diverged from the primitive placental stock, and apparently from 
the Insectivora in a more limited sense, at a very early date. Had 
such a sideHne evolved more rapidly, or had it run a longer span and 
occupied a more important place in mammalian history, it would be 
more conveniently defined as an order, as, for instance, are the tillo- 
donts, which probably had a very similar history but developed more 
striking specializations. Since, in fact, the mixodectids were a short- 
lived and relatively unimportant group, it is most convenient simply 
to classify them in the order Insectivora, from which they probably 
arose. 

Within the Mixodectidae there have been included two apparently 
distinct groups: Mixodedes and Indrodon of the Torrejon, on one 
hand, and Cynodontomys and Alicrosyops of the Lower and Middle 
Eocene, on the other. The Torrejon forms are certainly closely re- 
lated, indeed the distinction between them is not clear, and the Eocene 
genera are also closely allied and rather difficult to distinguish. 
Matthew (1915c) defined the two groups as subfamilies, Mixodectinae 
and Microsyopinae, and he repeatedly expressed doubts as to their 
really being related to each other, rather than merely convergent. 
In the lower jaw (the upper being uncertainly known in this respect) 
the "Mixodectinae" retain a canine, and the enlarged tooth is an 
incisor, while in the "Microsyopinae" there is only the enlarged tooth 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 129 

anterior to P^ The enlarged teeth are thus not rigidly proved to be 
the same, and with his customary caution Matthew stressed the fact 
that they might not be homologous. The premolars are different in 
the two groups, although I believe that the difference has been over- 
emphasized. In the "Microsyopinae" P*4 are less elevated and more 
molariform than in the "Mixodectinae." The molars are almost 
identical in the two groups, except that in the earlier forms there is a 
distinct and markedly internal hypocone, while in the later the 
hypocone is anomalously small and is less internal. 

The two genera discovered since Matthew's work, especially 
Eudaemonema, alter this situation. Eudaemonema has the anterior 
(lower) dentition less specialized than in Mixodedes, and Elpidophorus 
has it either closely similar to Alixodedes or slightly less reduced. In 
both cases there is no reason to beUeve that the enlarged incisor is 
not homologous with that of Mixodedes and also with that of Cyno- 
dontomys. In both genera P4 is submolariform. In Eudaemonema 
it is very similar to that of Cynodontomys and Microsyops, rather than 
to the contemporary Mixodedes. In Elpidophorus it is aberrant in 
having a strong, projecting paraconid. P* is not known in Eudae- 
monema; in Elpidophorus it closely resembles that of the Eocene 
genera. In Eudaemonema the upper molars have strong, internal 
hypocone, comparable to Mixodedes, while Elpidophorus is more 
like the Eocene genera in this respect. These genera thus mingle 
characters of the "Mixodectinae" and the "Microsyopinae", and 
they make it impossible to maintain a consistent separation between 
these groups. At the same time they strongly support the reahty of 
a relationship between them. 

For one reason or another the known Paleocene genera of this 
family cannot be considered ancestral to each other or to the Eocene 
forms. Thus Eudaemonema is the most primitive as regards the 
retention of anterior teeth, but its premolars are more advanced than 
in Mixodedes and Indrodon, and its strong, projecting hypocones seem 
to exclude it from the ancestry of Elpidophorus or of Cynodontomys 
and Microsyops. Mixodedes and Indrodon cannot be ancestral to the 
later forms for the same reason and cannot be structurally ancestral 
to the contemporary Eudaemonema because of their reduced anterior 
dentition. Elpidophorus has aberrant specializations in P4 and in 
details of molar structure that seem to exclude it from consideration 
as the ancestor of the Eocene genera. Evidently four different groups, 
intimately related but all on different lines of phyletic descent, are 
represented. These can be contrasted, among other details, by the 
characters listed in table 28. 



130 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

Table 28. — Comparison of dentition of six genera of Mixodectidae 



Genus 


Formula 


P4 


Interna] lower 
molar cusps 


F* 


Upper 
molars 


Mixodectes and 


1.1.3.3 


Elevated, paracon- 


Slightly or not 


Elevated, ex- 


With strong 


Indrodon. 




id minute, meta- 


taller than ex- 


ternal cone 


hypocones. 






conid rudimen- 


ternal. Meta- 


simple. 


projecting 






tary or absent, 


conid opposite 




internally. 






talonid poorly 


or slightly pos- 










basined with 2 


terior to proto- 










cusps. 


couid. 






Eudaemoncma.. 


2.1.4.3. 


About as tall as mo- 


About as in Mixo- 


(Unknown) 


About as in 






lars, paraconid 


dectes. 




Mixodectes. 






small, metaconid 












large, talonid 












well basined. 












with 3 cusps. 








Elpidophorus . . . 


1(+?). 1.3.3. 


With paraconid 


More definitely 


Less elevated, 


With weak hy- 






large and project- 


higher than ex- 


with separate 


pocones, not 






ing, otherwise 


ternal. Meta- 


paracone and 


projecting 






comparable to 


conid slightly 


metacone. 


internally. 






Eudaemonema. 


anterior to pro- 
toconid. 






Cynodontomys 


1.0.3.3 


Comparable to Eu- 


About as in Mixo- 


Comparable to 


Comparable to 


and Microsy- 




daemonema. 


dectes. 


Elpidophorus. 


Elpidopho- 


ops. 










rus. 



A possibility worthy of serious consideration is that the Phigio- 
menidae may be reLated to the Mixodectidae. They show the follow- 
ing principal characters suggestive of such a relationship: 

Molarization of premolars somewhat similar to mixodectids (except Mixodectes 
and Indrodon). 

Uppep molars with, feeble hypocone shelf and pronounced and peculiar median 
transverse valley (as in Elpidophorus and to a less degree some other mixodectids) , 
and otherwise generally but more vaguely similar. 

Tendency to emphasize external shelf of upper molars and to develop cuspules 
on it (but see below). 

Elevation of internal over external cusps of lower molars (a tendency in all 
mixodectids, pronounced in Elpidophorus) . 

Lines joining protoconid to metaconid and hypoconid to entoconid parallel and 
anterointernal-posteroexternal (tendency in mixodectids, pronounced in Elpi- 
dophorus). 

Paraconids, and trigonids generally, similar. 

Molar talonids markedly broadened. 

These, and a few minor details, produce a general type of dentition 
common to plagiomenids and mixodectids and not, as far as I know, 
to any other groups, ^^ 

" This was evidently partially noticed by Matthew (1918, p. 600), for he notes the resemblance to Ptagio- 
mene of "an undescribed genus from the Paskapoo beds", which was undoubtedly Elpidophorus, not then 
named and not until very recently known to be an aberrant mixodectid. 



FORT UNIOX OF CRAZY MOUNTAIN FIELD, MONT. 131 

On the other hand, the following characters show that the relation- 
ship cannot be very close, if it exists at all: 

Rather than a single mesostyle developed as a fold of the ectoloph, the plagio- 
menids have two independent median cusps on the outer shelf of the upper molars. 

The anterior incisors (in the lower jaw, at least) are not reduced in number and 
none is markedly enlarged. 

The hypoconulid does not have the characteristic mixodectid displacement 
toward the entoconid. 

The cheek teeth are all deeply furrowed and tend to proliferate cuspules. 

The inconclusive evidence of possible relationship of the plagio- 
menids to the Dermoptera has not been significantly altered since 
Matthew wrote (1918). The chain of evidence thus tending to link 
the mixodectids with the Dermoptera is so weak at every point as 
not to merit serious consideration at present. 

Genus EUDAEMONEMA Simpson 

Eudaemonema Simpson, 1935d, p. 231. 

Type. — Eudaemonema cuspidata Simpson. 

Distribution. — Middle Paleocene, Fort Union, Mont. 

Diagnosis. — Dental formula, 2.1.4.3. Median incisor enlarged. Canine 
larger than lateral incisor or Pi. Pi_2 small, 1-rooted. P4 submolari- 
form, with small paraconid, large, high metaconid, and basined, 
tricuspid talonid. Lower molars as in Mixodedes, but trigonids more 
elevated and all six cusps sharper and more distinct. Upper molars 
with prominent hypocones, projecting strongly internally. 

EUDAEMONEMA CUSPIDATA Simpson 

Figures 25, 26 

Eudaemonema cuspidata Simpson, 1935d, p. 231. 

Type. — U.S.N.M. no. 9314, left lower jaw with C, P2-M3, and roots 
or alveoli of all other teeth. Found by Dr. J. W. Gidley. 

Horizon and locality. — Gidley Quarry (referred specimen from 
Silberling Quarry), Fort Union, Middle Paleocene horizon, Crazy 
Mountain Field, Mont. 

Diagnosis. — Sole known species of genus. Dimensions in table 29. 

Remarks. — Alveoli in the type and roots in another specimen (no. 
9317) show clearly that there was an enlarged median incisor with a 
procumbent, laterally compressed root, flanked by one much smaller 
lateral incisor. The canine root is oval, implanted nearly vertically^ 
nearly as large as that of the median incisor, and much larger than 
that of either of the adjacent teeth. The crown is low, with a simple^ 
spatulate, recurved tip. Pi is not known, but its alveolus in three 
different specimens suggests that it was constantly present, although 
absent in all other known members of this family. Its root is single, 
small, and circular in section. 



132 



BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



P2 has a single but larger root. Its crown is simple, with one cusp, 
convex on the outer face and excavated anterointernally near the tip, 
followed by a small, mainly internal heel, not forming a definite cusp, 
P3 is larger and has two poorly separated roots. The anterointernal 
excavation is accentuated and tends to pinch off a very rudimentary 
paraconid, but there is no trace of a metaconid. The heel rises to a 
single, distinct cusp. P4 is nearly molariform. The paraconid is 
small but distinct and is median. The metaconid is nearly as high 
as the protoconid, with which it is partly confluent. The talonid is 
well developed, of about the same width as the trigonid, and has a 
large hypoconid and smaller entoconid and hypoconulid, the latter 
median. 





Figure 25.~Eudae'monema cuspidata Simpson, U.S.N.M. no. 9314, 
left lower jaw: a. Crown view; 6, internal view. Three times natu- 
ral size. 




Figure 26. — Eudaemonema cus- 
pidata Simpson, U.S.N.M. no. 
9558, left upper molars: a, Ex- 
ternal view; 6, crown view. 
Three times natural size. 



Mi_2 are closely similar to each other. The trigonid is moderately 
elevated and is narrower than the talonid. The paraconid is low and 
shelflike but is distinct and is united by a crest to the crescentic pro- 
toconid. The paraconid is about intermediate between the median 
and internal positions. The metaconid is slightly higher than the 
hypoconid, and the hypoconulid is lower and near the entoconid but 
more distinct from it than in Elpidophorus. All three talonid cusps 
are unusually lofty and distinct. A cuspule tends to develop on the 
hypoconid-metaconid ridge. M3 has the talonid narrower, about as 
wide as the trigonid, and the hypoconulid projects posteriorly and is 
higher than the other talonid cusps. 

Of the four specimens that show the posterior mental foramen, it is 
beneath P4 in two (including the type), is double with both under P4 
in another, and in the fourth is beneath P4 but is followed by another 
of much smaller size under Mi. In all cases the anterior mental 
foramen is larger, pronounced, and beneath P2. 



fORT UNIOX OF CRAZY M0UNTAI:N' FIELD, MOXT. 



133 



U.S.N.M. no. 9558, from the Gidley Quarry, is a left upper jaw 
with M^"^ It closely resembles Mixodectes, occludes well with some 
of the lower jaws of Eudaemonema cuspidata, and is not what would be 
expected in the upper jaw of any other known species, so that I place 
it here with some confidence. Aside from details of proportion, as 
shown in the figures, the outstanding differences from Mixodectes are 
the better development of the conules, especially the metaconule 
(almost lacking in Mixodectes), and the even greater internal displace- 
ment of the hypocone of M^. 

Table 29. — Measurements (in mm) of lower teeth of Eudaemonema cuspidata 



U.S.N.M. no. 


Pj 


Pa 


Pi 


Ml 


Mj 


Ms 




L 


w 


L 


W 


L 


W 


L 


W 


L 


w 


L 


W 


9314 


1.5 


1.3 


2.0 


1.4 


2.7 
2.6 
2.9 


1.9 
1.9 
2.0 


3.3 


2.7 


3.4 

3.5 
3.6 
3.8 
3.4 
3.5 


2.7 

2.8 
2.9 
2.9 
2.9 


4.0 
4.1 


2.6 


9313.. 




9317 






1.9 


1.5 


3.1 


2.6 




9sn 








9315 






1.9 


1.6 


2.7 

2.7 


2.2 
1.9 


3.0 
3.2 


2.7 
2.7 




9316 








9670 










2.4 



























Genus EI.PIDOPHORU.S Simpson, 1927 

ELPIDOPHORUS MINOR, new species 

Figure 27 

Type. — Princeton no. 14201, left lower jaw with P3-M2. Collected 
by A, C. Silberling. 

Horizon and locality. — Probably Silberling Quarr^^, Fort Union, 
Middle Paleocene horizon, Crazy Mountain Field, Mont. 

Diagnosis. — Smaller than E. elegans or E. patratus. P^ slenderer 
than in E. patratus, paraconids P4-M2 more strictly internal, heel of P4 
smaller and less strongly basined, elevation of inner cusps P4-M2 
distinct but slightly less pronounced than in E. patratus. 

Remarks. — The type and only known specimen was found by Silber- 
ling on January 18, 1903, and is labeled as from the Torrejon, LocaUty 
No. 2 (not of the serial list later started and employed in this work). 
Mr. Silberling states that these data mean the No. 2 beds at or near 
the Silberling Quarry. It is extraordinary that no further material of 
this pecuhar form seems to occur in the much larger collections made 
subsequently. 

The species is very distinct from the later E. patratus of this field, 
and it will probably prove to be generically different, but they are 
certainl}^ alUed and the present data do not seem to warrant generic 
definition. E. minor resembles Eudaemonema more than does E. 



134 



BULLETIN 169, UNITED STATES NATIONAL MUSEUM 



patratus, but it is closer to the latter than to E. cuspidata and shows the 
Elpidophorus line to have been distinct at this time. 

Dimensions of the type are as follows: Length P3, 2.0; width P3, 1.4; 
length P4, 2.7; width P4, 1.9; length Mi, 2.8; width Mi, 2.6; length 
M2, 3.0; width M2, 2.8. 




Figure 27 .—Elpidophorus minor, new specie?, Princeton Univ. no. 14201, left lower jaw: a, Crown view; &, 
internal view. Six times natural size. 

7INSECTIV0RA, incertae sedis 

PICRODONTIDAE, new family 

Type. — Pier odus 'Douglass, 1908. 

Distribution. — Middle and Upper Paleocene, North America. 

Diagnosis. — -Minute insectivoreUke or batlike forms of doubtful 
ordinal affinities, with one pair of greatly enlarged incisors (at least 
in lower jaw), muzzle long and slender, canines reduced, premolars 
small with no tendency to molarization, molars large, brachyodont, 
with shallow, expanded basms and indistinct cusp structure, adaptively 
resembling molars of the recent Phyllostomatidae. 

Discussion. — At present only two genera, Picrodus and Zanycteris, 
are referred to this family, and these are not directly comparable with 
each other. The evidence for their close relationship is, however, 
impelling, as discussed below. The separation of family characters- 
from those merely generic is not entirely practicable in this stage of 
knowledge, but there can be Httle doubt that these two genera do 
belong to a family otherw^ise unknown, and the characters given in 
the above diagnosis distinguish them from any other family. The 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 135 

molars invite comparison with the Phyllostomatidae, although they 
do not prove that a real relationship exists. The character of the 
antemolar dentition distinguishes the Picrodontidae sharply not only 
from the Phyllostomatidae but also from all other Chiroptera. 

The affinities of the Picrodontidae are wholly dubious at present. 
They compare in a very broad and general way with the Insectivora, 
Chiroptera, and Primates. Reference to the Primates is merely a 
possibility, with no positive evidence to commend it. Evidence for 
reference to the Chiroptera is seen in the phyllostomatidlike molars 
but is reall}^ very tenuous and does not at present warrant the extraordi- 
nary conclusion that the Chiroptera had already in the Middle Paleo- 
cene achieved tliis peculiar and aberrant molar pattern and at the 
same time had lost, or not yet acquired, characters otherwise universal 
among chiropterans. Such references, even when circumspectly 
expressed, are moreover likely to be misleading, for they inevitably 
are restated in more general works by authors not acquainted with the 
original material, in some such form as "Specialized phyllostomatid 
bats were already present in North America in the Middle Paleocene", 
without the necessary addition that the evidence actually falls far 
short of proof. It is more conservative and less prejudicial to future 
work to refer the Picrodontidae to the ?Insectivora, using Insectivora 
in its scrap-basket sense, pending discovery of more conclusive indica- 
tions of affinity. When these are discovered, they are (as far as can 
be foreseen) as hkely to point to the Insectivora as to any other order. 

Genus PICRODUS Douglass, 1908 

Picrodus Douglass, 1908, p. 17. 
Megopterna Douglass, 1908, p. 18. 

Type. — Picrodus silberlirigi Douglass. 

Type o/ Megopterna. — Megopterna minuta Douglass. 

Distribution. — Middle Paleocene, Fort Union, Montana. 

Diagnosis. — Enlarged, procumbent anterior lower tooth, followed by 
three or four small teeth, the most posterior (P4?) 2-rooted but small 
and simple. Mi much enlarged, with a small, elevated, and procum- 
bent trigonid with three poorly differentiated cusps, heel elongate and 
large, with a curving crest and two vague internal cuspules, basin not 
closed. AI2 with lov/er, subquadrate but 3-cusped trigonid, large, oval, 
basined talonid with crest and two internal cusps. Enamel of both 
talonids papillated. 

Remarks. — From Douglass' specimens and, still more, his some- 
what diagrammatic figures it would appear altogether impossible that 
Picrodus and Megopterna should be synonymous, but this is shown to 
be true bej^'ond any question by the larger series of specimens now 
available. The type of Picrodus included P4 and Mi, the latter im- 
perfect, and that of Megopterna included M2 and a small fragment of 
119212—37 10 



136 BULLETIN 16 9, UZS^ITED STATES NATIONAL MUSEUM 

Ml that Douglass mistook for a complete tooth. The type species 
are synonymous. 

Douglass referred Picrodus questionably to the Epanorthidae 
(=Caenolestidae) and Alegopterna questionably to the Insectivora, 
without family reference. The resemblance to caenolestids is con- 
fined to a vague adaptive similarity to some fossil forms with enlarged 
Ml and is not indicative of affinity. Picrodus is almost certainly a 
placental mammal. Among placentals, however, I am not acquainted 
with any genus with which close and direct comparison is possible. 
There is, indeed, a vague resemblance to certain liighly speciahzed 
recent bats, but this does not extend to structural details, is contra- 
dicted by the quite different arrangement of the anterior dentition, 
and is more likely to be misleading than not. 

There is one known genus, Zanycteris, with which Picrodus is almost 
certainly closely related, although direct comparison is impossible 
since in Picrodus only lower and in Zanycteris only upper teeth are 
known. As I have elsewhere noted (Simpson, 1935a), Zanycteris 
(like Picrodus) resembles some recent bats, particularly the phyllo- 
stomatids, in adaptive characters of the cheek teeth but is different 
in details probably of more importance as indices of affinity and in 
the structure of the anterior dentition, as far as it is known. The 
great probabihty of affinity between Picrodus and Zanycteris is inde- 
pendent of the possibility that they are related to the Chiroptera. 
In Zanycteris the reduction and complete lack of molarization of the 
premolars, the enlargement of M^ and reduction of M^, and the peculiar 
papillated coronal enamel are all unusual specializations analogously 
developed in the lower dentition of Picrodus. Furthermore, even in 
detail the shapes of M^"^ in Zanycteris adapt them perfectlj^ for occlu- 
sion with lower teeth like those of Picrodus. Zanycteris paleocena 
will not occlude with Picrodus silhejiingi, being a smaller species, but 
probably a dentition structurally the same as that of Zanycteris but of 
different size would occlude with Picrodus silherlingi. Zanycteris is 
known only from one specimen found in the Tiffany, Upper Paleocene, 
of southwestern Colorado. Its type is certainly not the same species 
as that of Picrodus, and the genera are probably distinct, but not 
surely. Knowledge of their exact affinities must await discovery of 
upper teeth of Picrodus or lower teeth of Zanycteris. 

PICRODUS SILBERLINGI Douglass 

Figure 28 

Picrodus silherlingi Douglass, 1908, p. 17. 
Megopterna minuta Douglass, 1908, p. 18. 

Tyjpe. — Carnegie Mus. no. 1670, right lower jaw with P4-M1. 
Collected by A. C. Silberling. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 137 

Type oj Megopterna minuta. — Carnegie Mus. no. 1675, left lower 
jaw with M2 and part of talonid of Mi. Collected by A. C. Silberling. 

Horizon and locality. — Types from Silberling Quarry, most referred 
specimens from Gidley Quarry, Fort Union, Middle Paleocene horizon, 
Crazy Mountain Field, Mont. 

Diagnosis. — Sole known species of genus. Dimensions given below. 

Remarks. — From alveoli it is clear that this species had a much 
enlarged, procumbent anterior tooth, probably an incisor, with a 
compressed root. U.S.N.M. no. 9866 includes Mi of P. silberlingi 
and also a loose tooth, which probably is an associated lower incisor. 
It has a completely enameled crown, curving sharply to a point. The 
whole crown has a series of eight or nine ridges or angulations, diverg- 
ing posteriorly from the apex, so that in transverse section it is 
irregularly polygonal. Aside from these, one side is more convex, the 
other somewhat excavated, ^vith a slight basal cingulum. 




Figure 2i.—Picrodus silberlingi Douglass, U.S.N.M. no. 9622, right lower jaw: a, Crown view; 6, external 

view. Four times natural size. 

The anterior"tooth is followed by three small, closely spaced, ap- 
proximately equal alveoli. The material does not indicate whether 
these were for three separate teeth or for one 1-rooted tooth and 
one 2-rooted. The next tooth, presumably P4, has two roots in the 
several specimens that show it, not one as stated by Douglass for the 
type. It has a simple main cusp, more procumbent than shown in 
Douglass' figure, followed by a small heel. The next tooth, pre- 
sumably Ml, is the largest in the jaw and is very peculiar. It differs 
considerably from Douglass' figure, although I believe that the pres- 
ent specimens do belong to his species and that the discrepancy is 
due to the worn and broken nature of his specimen and the impos- 
sibility of accurate observation except under a binocular microscope 
at magnifications of 15 or 20 X. This tooth consists of a trigonid and 
talonid, but both are greatly modified. The trigonid is small and is 
produced and procumbent, as if drawn forward and upward in a 
plastic condition. The protoconid lies near the midhne of the tooth 
as a whole. The metaconid is slightly lower, poorly separated from 
the protoconid, and internal and sHghtly posterior to the latter. The 



138 BULLETIN 16 9, ITXITED STATES NATIONAL MUSEUM 

still lower and likewise poorly separated paraconid is almost directly 
anterior to the protoconid but slightly more internal. The talonid is 
wider than the trigonid and is very long. It has a crest that begins 
rather indefinitely on the external side against the base of the trigonid 
and curves back to the posterointernal corner of the tooth. Its 
highest part is where it swings internally and across the midline of 
the tooth, and here it bears two or three vague cuspules. There are 
also two small cuspules on the inner margin of the talonid, separate 
from the crest and at a lower level. The more definite of these is 
just anterior to the posterointernal corner, and the other vague cusp 
lies between this and the metaconid base. The sloping and volute 
surface of the talonid, from the crest down to the inner margin, is 
finely papillated and wrinkled. The lowest point of this surface is. 
at the posterointernal corner, where there is an almost spoutlike exit 
from the vague talonid basin. 

M2 was figured by Douglass {"Megopterna minuta"), but his draw- 
ing makes the cusps appear more upright, sharp, and distinct than 
they really are. The trigonid suggests that of Mi but is much les& 
elevated, the cusps are better separated, the paraconid is more inter- 
nal, and the trigonid is given a more quadrate form by the angulation 
of the crest connecting protoconid and paraconid. The talonid is 
broad and oval, less sloping and more distinctly basined than that of 
Ml. The crest defines the posteroexternal angle, instead of curving 
obliquely across the tooth as on Mi, and there are two distinct inter- 
nal cusps, the more posterior of which is connected to the crest. The 
basin surface is papillated as on Mi, 

M3 is not preserved on any specimen in the collection. From its 
alveoH, it was smaller than M2, Upper teeth have not been recog- 
nized. 

From the downward curvature of the low^er margin posterior to the 
dental region, it is evident that the angle was of placental type. The 
mental foramina are numerous and variable. There may be a cluster 
of three or four in the general region of P4. The most constant 
appear to be a fairly large foramen approximately between P3 and P4 
and a smaller one about between P4 and Mi. 

The type is not well preserved, and I have not remeasured it. It 
may be slightly larger than the other specimens, but there is no doubt 
that all are conspecific. The most reliably measurable dimension is 
the oblique maximum diameter of Mj, that is, a dimension in the 
midline in a vertical (but not also a horizontal) plane, from paraconid 
to base of posterior end of talonid. ^^ The constants of this dimen- 
sion in the National Museum sample are: N, 8; R, 2.6-2.9; M, 
2.71 ±0.04; a, 0.105 ±0.026; V, 3.9 ±1.0. The width of this tooth 

«6 The ordinary length, a horizontal between transverse, vertical tangential planes, would show great 
subjective and accidental variation in such a small and peculiarly oblique tooth. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 139 

is not SO accurately measurable but is recorded A\athin the range 1.0 
to 1.3, mean 1.16, for these eight specimens. P4, poorly preserved 
and very difficult to measure, has a maximum oblique diameter of 
about 1 mm and a width of 0.6 or 0.7 mm. M2 is well preserved only 
in the type of Megopterna minuta, where it is 1.4 mm in length and 
about 1 mm in wddth. The less completely preserved specimens of 
this tooth do not suggest a deviation of more than 0.1 mm from this. 
The one Silberling Quarry specimen in the National Museum col- 
lection has Ml with the dimensions 2.8 and 1.1, well within the range 
of the Gidley Quarry material. 

Family Uncertain 
Genus and species undetermined 

Figure 29 

U.S.N.M. no. 9777, from the Gidley Quarry, is a right humerus 
of a fossorial mammal of about the size of a recent Scalops. It is 
imperfect but preserves highly characteristic features. The laterally 
compressed head, short, stout, twisted shaft, and flattened, widely 
flaring distal end are disposed in such a way that if the head was 
directed posteriorly, the entepicondyle was anterior and only very 
slightly internal in position, and the ectepicondyle similarly posterior, 
«o that the lower arm was throv/n outwards almost at right angles 
to the body. The bicipital groove, mainly occupying the proximo- 
internal quarter of the posterior face, is deep and narrow, bounded 
by sharp crests and elevated tuberosities, which are, however, broken 
off. The pectoralis major insertion is broad and shallow, occupying 
most of the proximal half of the anterior face of the shaft, and not 
sharply bounded distally. The deltoid process is broken, but from 
its base it was more prominent and more internal than in Scalops, 
more proximal and heavier than in Arctorydes. The notch between 
head and ectepicondyle is nearly semicircular. The distal end has 
greatly produced epicondyles, the extension of the ectepicondyle far 
beyond the globular capitulum being especially striking, in comparison 
with Scalops. The other distal articulations are poorly differentiated 
or preserved. The entepicondylar foramen is strangely developed as 
a long, small canal, running from the posterior face near the internal 
margin to the middle of the anterior face of the broad distal end. 

This peculiar humerus resembles those of recent moles in many 
respects but also differs throughout in detail. Unquestionably the 
resemblance bespeaks similarity of habits. Whether it also indicates 
phylogenetic affinity is quite uncertain. In some respects resemblance 
is closer to Arctorydes from the Ohgocene (see Schlaikjer, 1933), but 
there are also numerous differences: The distal end is more nearly 
parallel to the long (anteroposterior) axis of the head; the deltoid 



140 



BULLETIN 16 9, UNITED STATES NATIONAL. MUSEUM 



process is less internal, stouter, and more proximal; the ectepicondyle- 
is more produced; the entepicondylar foramen, or rather canal, is 
longer; and other differences of proportion and detail are seen. Never- 
theless a relationship seems probable. The Ardorydes humerus was 
supposed by Matthew to belong to a chrysoclilorid, but Schlaikjer 
has shown that the e^^dence is all against this view and favors talpid 
affinities. Ardorydes may belong with the dentitions and skulls 
known as Proscalops. 




Figure 29. — Humerus of an unidentified fossorial mammal: a, Anteroexternal face; 6, posterointernal face-. 

Four times natural size. 



On the basis of the teeth, no genus known from the Gidley Quarry 
w^ould seem to be closely allied to Proscalops. Some nyctitheriids 
have been supposed to be talpids or at least talpoids, but the only 
probable nyctitheriid in this fauna, Stilpnodon simplicidens, is too 
small to have had this humerus. The humerus does not belong to a 
multituberculate nor to any other order known in this fauna save the 
Insectivora. It is not leptictid and cannot belong to Aphronorus if 
that genus is really a pantolestid, but might if the genus does not 
belong with Palaeosinopa and Pantolestes. It might belong to Gela- 
stops but probably does not if that genus is correctly considered an:' 
ally of Didelphodus. Eudaemonema shows some, but only very 
distant, resemblance to such dentitions as Proscalops and might 
conceivably have had a fossorial humerus. The dentition of the' 
animal represented by this humerus may be unknown, although this 
is improbable in view of the many jaws and few humeri collected 
from the quarry. 

In any event the presence of such a specialized fossorial animal in 
this ancient fauna is of great interest. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 141 

Order PRIMATES Linnaeus, 1758 

The Fort Union primates are of exceptional interest as the oldest 
known members of the order to which man belongs, and any light 
that they can cast on the early history of this great group is highly 
important. Dr. Gidley fully recognized these facts, and when the 
arduous task of preparation was finally completed, he turned first to 
the primates in beginning his definitive work. His previous papers 
were all prehmmary and provisional, but he completed the primate 
section of his proposed memoir and published it in 1923 as a separate 
paper, later to be united with the other proposed sections into a 
single monograph. No other section was ever finished, and the pri- 
mate paper was Gidley's last contribution to the Paleocene." 

When these primates were discovered they were far the oldest 
laiown. Many primates were known from the Eocene of Europe 
and North America, but only one, Plesiadapis, was known from the 
Paleocene, and this was considered as only very doubtfully primate 
and is considerably younger than the Fort Union primates of Gidley's 
collection. After Gidley's discovery, but before its publication, 
Matthew (1915) added Nothodedes (—Plesiadapis) also from the 
Paleocene, and in 1921 Matthew and Granger added several more 
genera from the Tiffany, but these are all younger than Gidley's 
material. Jepsen and I have made recent additions to the known 
upper Paleocene primates, but only Plesiolestes Jepsen, 1930, is of an 
age comparable to Gidley's genera, and there is no reason to suppose 
that it is older.^^ 

It is in accord with Gidley's intention that these forms are here 
redescribed in connection with the whole fauna, despite their publica- 
tion previously. Tliis is the more necessary because since Gidley's 
publication knowledge of early primates has been greatly increased 
both by discovery and by revision, calling for reconsideration of many 
points that he mentioned. For tliis reason, his diagnoses and discus- 
sions are not quoted in full, but are revised in the light of the wider 
knowledge of today and of the somewhat different conclusions to 
which tliis has led me. 

Gidley recognized four new genera in this fauna and placed six 
species in them. The fact that two species are based on upper jaws, 
with lowers referred, and the other four on lower jaws, with uppers 
referred to three of them, introduces a slight element of doiibt, but on 
the basis of the lower jaws, at least, it is certain that six species are 
represented and that Gidley's identifications of aU these specimens are 

" With the minor exception of a very brief note on the Tiffany. 

5* Abel (1931) lists Plesiolestes as from the Lower Paleocene and suggests that it is the oldest knowik 
primate, but it is from the middle Paleocene and not appreciably, or not at all, older than the genera here 
discussed, one of which it closely resembles. 



142 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

correct. The only taxonomic change to be introduced is that a fifth 
genus is made to receive a species that Gidley placed doubtfully in 
Palaechthon. 

Family ?ANAPTOMORPHIDAE Cope, 1883 

In this fauna the three genera Paromomys, Palaechthon, and 
Palenochtha are very tentatively listed with the Anaptomorphidae, 
although (as will appear) the relationship is not clear and tliis whole 
complex of early primates is highly polyphyletic and very confusing. 

Paromomys, Palaechthon, and Palenochtha evidently belong to 
slightly divergent lines, but they have certain characters in common. 
The most important of these are: 

1. An enlarged, semiprocumbent lower incisor, its root not extending beneath P^. 

2. Other lower incisors vestigial and variable or absent. 

3. Lower canine present and only slightly reduced. 

4. Pi and probably sometimes P2 absent.^^ 

5. P4 little or not enlarged, trigonid simple, elevated, with low, 2-cusped talonid. 

6. Molar trigonids with small, generally short and quadrate basins, paraconids 
generally distinct but reduced, cusps marginal or nearly so. 

7. Heels of Mi_2 large, simple, broadly basined. 

8. M3 with third lobe, which, however, differs greatly and characteristically in 
the three genera. 

9. P^ (as far as known) 2-rooted and not transverse. 

10. P^ transverse, strong protocone, paracone and metacone little or not differ- 
entiated, conule feeble or absent. 

11. Upper molars without mesostyle, protostyle, or hypocone; two small but 
distinct conules; posterointernal corner of crown expanded and basined to varying 
degrees; inner face of molar with vertical groove at least on IVP. 

These suggest a possible fairly immediate common origin for the 
three genera, but they are diverging from each other, principally as 
follows: 

Paromomys: Antemolar dentition of unmodified basic type as listed above- 
Molar trigonids very short and quadrate, paraconid almost disappearing by fusion 
with metaconid on M2-3. Third lobe of M3 very strong, with at least two distinct 
cusps. Inner base of M^, at least, more or less bilobed. Posterointernal expan- 
sion of upper molars very marked. 

Palaechthon: P4 more progressive, with distinct paraconid and metaconid. 
Molar trigonids less quadrate and paraconids more distinct. Third lobe of M3 
weaker but still with two cusps. Upper molars not bilobed, posterointernal expan- 
sion less. 

Palenochtha: Anterior dentition further modified by loss of another tooth, prob- 
ably P2. P4 much as in Paromomys. M3 with weak, 1-cusped third lobe. Upper 
molars not bilobed, posterointernal expansion slight. 

Except for the absence of P2 (which, however, is not absolutely cer- 
tain), Palenochtha seems definitely the most primitive of the three and 
its general structure is such as might be expected in the ancestry of 

58 Certain homologies, discussed on a later pa!;e, are here assumed. Exact identification is impossible, but 
as the teeth are probably homologous between the genera in question, if they are labeled consistently it does 
not matte from the point of view of determining affinities whether the labels prove to be correct or not. 



FORT Ui^ION OF CRAZY MOUNTAIN FIELD, MONT. 143 

both the other genera. Paromomys and Palaechthon show crossing 
speciahzations. The general molar structure of Palaechthon is 
specialized more or less in the direction of Paromomys but is less aber- 
rant, while its P4 is definitely more progressive. Paromomys shows 
distinctly the most aberrant molar structure but has P4 still relatively 
unprogressive. 

The only known primate of comparable age is Plesiolestes Jepsen, 
from a Torre j on equivalent in the Fort Union of northern Wyoming. 
Its age is not appreciably different from that of the Gidley Quarry spec- 
imens, and the geographic locality is not very distant, all occurring in 
the same widespread formation. Jepsen tentatively referred his 
genus to the Plesiadapidae but noted (1930a, p. 506) liiat "there are 
many structures on the two specimens which are not like those of other 
Plesiadapids." He did not compare with Gidle3^'s previously pub- 
lished genera, which Plesiolestes resembles in many ways. The 
anterior alveoli show an enlarged semiprocumbent incisor and a 
smaller, less procumbent canine, as in all three of Gidley's genera 
here discussed, and also a moderate P2, as in Paromomys and Palaech- 
thon. P3 is also closely similar, but relatively larger, being about as 
high as P4, whereas in Gidley's genera it is lower. P4 closely resembles 
that of Palaechthon, the only difference clear from the available data 
being that in Plesiolestes the heel is wider and the paraconid and meta- 
conid stronger, especially the latter. The molars are very similar to 
those of Palaechthon and seem to me to show no difference of probably 
generic value. 

While Plesiolestes may be provisionally accepted as valid, chiefly on 
the basis of the more progressive P4, it is almost surely very closely 
related to Palaechthon, and the distinction of the genera is not at pres- 
ent wholly satisfactory. If, as is possible, Plesiolestes is somewhat 
younger, it could well be a slightly modified and progressive descend- 
ant of Palaechthon. Its diagnostic features, as against Palaechthon, 
seem to me modifications away from as much as toward the plesiada- 
pids. In any case it is surely closer to Palaechthon than is either genus 
to any undoubted plesiadapid, and if a plesiadapid relationship exists 
at all, Palaechthon is probably less removed from that line than is 
Plesiolestes. 

Palenochtha, the least aberrant of the present genera as regards 
comparison with an abstract protoprimate dentition, seems to resemble 
the Eocene tarsioids (in the broadest sense) more than any other 
known mammals. The specialization of the anterior lower teeth is 
not exactly as in any later tarsioid but is within the apparent poten- 
tiaUties of the group. Omomys, from the Bridger,^° has two enlarged 

«« The American lower Eocene species placed in Omomys are very doubtfully congeneric with the Bridget 
genotype. As noted by Teilhard, the European lower Eocene specimens are very distinctive and might 
be, in my opinion definitely are, representative of a different genus but one close to and perhaps structurally 
ancestral to true Omomys. 



144 BULLETIlSr 16 9, UNITED STATES NATIONAL, MUSEUM 

anterior teeth followed by three premolars, but in it there is a small 
tooth between these two enlarged teeth, which is either much more 
reduced or wholly absent in the much older Fort Union genera. 
Absarokius may very closely resemble the Fort Union genera in the 
anterior teeth, although this is very dubious, as they are known in 
Absarokius only from poorly preserved alveoli of one specimen, which 
seems to show less disparity between the incisor and the ?canine. 
Tetonius and the European Necrolemur have a single enlarged anterior 
tooth,^^ a condition that could be derived from that of the middle 
Paleocene genera, although there is no adequate evidence that it was 
so derived. 

P4 is more primitive in Palenochtha than in any later tarsioid genus 
known to me, but the difference in such forms as Anaptomorphus or 
^'Omomys" belgicus is not marked, and as the increasing and diverg- 
ing specialization is in keeping with the relative ages it has no crucial 
bearing on general affinities. The lower molars of Palenochtha are 
much like those of Wmomys vespertinus, "Omomys" belgicus, and simi- 
lar forms, that is, those Eocene tarsioids in which the molars are least 
specialized. The same may be said of the upper molars: those of 
Palenochtha show distinctions by which the genus may be recognized 
(such as the internal groove and more inclined protocone), but they 
very closely resemble the least aberrant Eocene tarsioids. Compari- 
son with Wmomys vespertinus is especially suggestive of affinity. Most 
later genera differ in the manifestly progressive development of sec- 
ondary internal cusps. 

It is, incidentally, worthy of note that Palenochtha has no known 
character that would exclude it from ancestry to Tarsius, itself, 
although of course the absence of intermediate stages makes this ob- 
servation unworthy of being advanced except as an interesting but 
wholly untested possibility. 

The more advanced P4 of Palaechthon does not call for detailed con- 
sideration. It is in line with progressive changes in many tarsioids 
■and some other primates, although it should be noted that the devel- 
opment of P4 in the Tetonius, Carp>olestes, Apatemys, Plesiadapis, and 
some other groups lies along distinctly different lines. 

The peculiar molar structure suggested in Palaechthon and fully 
developed in Paromomys is more distinctive. The short quadrate 
trigonid and marginal paraconid approximated to the metaconid 
appear among tarsioids in only one or two later genera. Absarokius 
has very similar trigonids on M2-3, but that of Mi is more elongate, 
probably secondarily in connection with the shearing development of 
P4. Other American tarsioids are more distinctive. Among European 
forms, only Necrolemur and Microchoerus are similar, and they are 

61 Commonly called the canine, but it seems to me more probable that it is an incisor in both cases. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 145 

3iiore advanced in the reduction of the paraconid, but are much 
younger. The broad third lobe of M3 and double hypoconulid also 
appear in Necrolemur and Microchoerus , but not in Ahsarokius. Among 
American tarsioids only Washakius has a similar talonid on M3, and 
its trigonids are quite different. 

The characteristic posterointernal upper molar expansion and basin- 
ing of Paromomys are suggested in many later tarsioids, such as 
Jibsarokius, Hemiacodon, Shoshonius, Tetonius, and, in Europe, Nanno- 
pithex (most marked in Ahsarokius and Nannopithex) , but in all these 
the structure is much less marked. In some cases (e. g., Tetonius) it 
is so slight that it is noted only by special search with Paromomys in 
mind, and in all the instances mentioned there is the characteristic 
distinction that a posterior cingulum passes internally beyond the 
limits of the incipient (or vestigial) basin and tends to form a hypocone 
at its inner end. This could be a specialization from the Paromomys 
^condition, but the difference is clear and there is no evidence of cer- 
tainly intermediate stages. In the European Necrolemur (and its 
highly modified ally, Microchoerus), however, the hypocone is on the 
Tim of a basin much like that of Paromomys, and structural ancestry 
as regards this character is quite possible but hypothetical. 

In summary comparison with the acknowledged tarsioids, there are 
Tcsemblances throughout and every separate structure of the Fort 
Union genera is approached in some later genus. The fundamental 
rsimilarity is most clear in Palenochtha, but even in tliis most general- 
ized type the anterior dentition is too specialized for ancestral rela- 
tionship to any known later genera but Tetonius, Necrolemur, Micro- 
-choerus, and (still more doubtfully) Ahsarokius, and in these cases the 
minor morphological differences are also marked and annectant forms 
unknown. Paromomys and Palaechthon also resemble various later 
-genera, but in most cases crossing specializations make any approach 
to direct phyletic connection impossible. Ahsarokius is, on the whole, 
the most similar American form, but in several respects it is apparently 
less specialized ; for instance, in the simpler heel of M3, probably less 
-enlarged incisor, and smaller protocone of P* (which may, however, be 
secondary), despite its younger age. 

The European genus Necrolemur ^^ compares more closely with 
Paromomys than does any known tarsioid to the extent that it exhibits 
all the principal speciahzed characters of Paromomys and that while 
it has numerous additional specialization of its own, no crossing special- 
zation is involved. Its dental formula is probably frijj. Stehlin 
(1916) has placed this upper formula beyond any serious question. 
He gives the lower formula as ^yixi; but the evidence is very uncon- 
vincmg. A priori it is highly improbable that an enlarged median 

"The following remarks apply equally to Microchoerus, excppt that the latter is much more highly special- 
ized in the dentition. If Necrolemur comes from Paromomys, then, ipso facto, Microchoerus does also but 
has evolved more rapidly. 



146 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

tooth should be a canine, that Pi should be present in an upper Eocene 
tarsioid when it is absent, as far as surely known, in every other laiown 
tarsioid even in the Paleocene, or that an enlarged lower canine should 
occlude against an enlarged first upper incisor and anterior to a second 
upper incisor. The occlusion in itself is so suggestive of an incisor 
that only the strongest contrary evidence would warrant any other 
conclusion, and the other considerations seem to place this almost 
beyond doubt. It is true that in Tarsius the largest anterior mandi- 
bular tooth is the canine, but as Stehlin (1916) himself has shown the 
analogy with Necrolemur is very distant, and in Tarsius the lower 
canine occludes between I^ and C as would be expected, not between 
I^ and I^. Furthermore, the actual formula in Tarsius is yjj;^, as 
I believe it was also in Necrolemur. ^^ 

If this formula be accepted for Necrolemur, its anterior dentition 
could be derived from that of Paromomys by further enlargement of 
the already enlarged incisor and great reduction of the canine, still of 
moderate size but not enlarged in Paromomys. The premolars of 
Necrolemur are broader, lower, and more proclivous than in Paro- 
momys, and there is a distinct metaconid on P4. The lower molar 
structure is closely similar throughout except for details in Necrolemur 
like the complete loss of separate paraconid on M2.3, which are the 
logical continuation of tendencies clearly present in Paromomys. 

In the upper jaw, the 3-rooted P^ of Necrolemur is also progressive. 
P* and the molars are less transverse than in Paromomys, a feature of 
no clear significance. The protocone of P* may be smaller in the 
later genus; if so, it is the only character that suggests, and it does 
not prove, that Necrolemur could not be derived from Paromomys. 
Aside from their proportions, the upper molars of Necrolemur dift'er 
in having stronger conules (the metaconule double) and distinct 
hypocones, but the basic plan is remarkably similar, as already 
suggested. 

As far as the dentition goes, it must be concluded that Necrolemur 
and Paromomys are probably rather closely related, and the latter 
could be ancestral to the former. The conclusion is obviously un- 
proved and open to doubt. Corresponding with their great separation 
in space and in time, the genera do differ markedly and annectant 
types are unknown, but the fundamental similarity is striking. 

Trogolemur, Uintalestes, and Phenacolemur are all incertae sedis;, 
but all show some special resemblances to Paromomys and its Fort 
Union allies. Trogolemur has the same dental formula as Paromomys, 
jx^. The incisor is relatively larger, and the next tooth, presum- 
ably the canine, is very small. The premolars are more expanded 

«' Although the ease is less clear, by analogy it seems probable that the enlarged median mandibular 
teeth of Tetonius are also a pair of incisors, not canines as generally supposed following Matthew. I should 
write the Tctov'ms formula either 1.0.3.3 or 1.1.2.3, of which the second is perhaps slightly more probable. 
(Matthew wiote 0.1.2.3 but this is an evident lapsus, and he clearly meant to write 0.1.3.3-) 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 147 

transversely but otherwise similar. P4 has a metaconid. M1.2 are 
much like Paromomys. The third lobe on M3 is narrower than in 
P. maturus but closely approached in P. depressidens. The cheek 
teeth throughout are very close to Palaechthon but lower, broader, 
and heavier. Palaeddhon is an admirable structural ancestor for 
Trogolemur, although the time gap is too great for definite decision. 

Uintalestes is very poorly known but is evidently related to Tro- 
golemur from which it differs essentially only in the further dental 
reduction, having only seven teeth in the lower jaw, and the narrower 
heel of P4. 

The lower molars of Phenacolemur could readily be derived from 
the Paromomys type but are heavier and more quadrate. P4 is also 
similar but is much enlarged and likewise heavier and more quadrate. 
The much heavier incisor and the complete loss of all teeth between 
it and P4 sharply distinguish Phenacolemur, however, and the time 
gap is far too short for derivation from Paromomys. The molar 
resemblance may, therefore, be misleading. P^ has a much stronger 
posteroexternal cusp than in Paromomys, and the internal groove is 
absent on the upper molars, but they have an equally and similarly 
expanded posterointernal basin and in general are as close to those of 
Paromomys as are the lower molars. 

Resemblances to the Carpolestes and the Plesiadapis phyla are dis- 
cussed in dealing with the contemporary members of the latter, 
Elphidotarsius and Pronothodectes , but the adaptively related group 
Apatemyidae has no known representative before the upper Paleocene. 
They may, however, be summarily dismissed as possible close relatives 
of the Fort Union forms, as none of their peculiar distinctions are 
foreshadowed in the latter. The apatemyids, as redefined by Jepsen 
(1934), have an enlarged incisor, larger than in Carpolestes or Plesia- 
dapis, which more nearly resemble Paromomys and its allies in this 
respect, and early lose all teeth between this and P3, at least two of 
which are retained in Paromomys and in the other two groups men- 
tioned. P3 becomes 1-rooted and pecuHarly bladed. P4 is markedly 
reduced even in the upper Paleocene and becomes vestigial in later 
forms. The molars have a quadrate trigonid, as in many early 
primates, but, especially on Mi, it is much more elongate anteropos- 
teriorly than in Paromomys and its allies. The upper teeth are 
equally divergent. 

Gidley (1923, pp. 3-4, 8-9) noted the resemblance of Paromomys and 
Palaechthon to the Notharctinae in the lengthened heel of M3, the 
trigonids consisting chiefiy of protoconid and metaconid connected 
by a loph and with an anterior shelf, and the posterointernal expan- 
sion and basining of the upper molars. He added, however, that 
these are not exclusively notharctine characters and concluded that 
they did not indicate close affinity in this case. The resemblance is. 



148 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

indeed, very close, and as far as the posterior teeth are concerned the 
differences involve only a few minor details of apparent generic or 
lesser value. The anterior teeth, however, are very different and are 
much more specialized in the earlier genus. Pelycodus has the formula 
^xza as against yj:^^ in Paromomys and Palaechthon, its incisors 
are small and its canine large. Furthermore, the Paromomys-like 
molar characters of Pelycodus are not seen in Adapis, but the Notharc- 
tinae, to which Pelycodus belongs, and the Adapinae show a funda- 
mental resemblance in skull and skeletal structure, which leads 
(Gregory, 1920, and elsewhere) to their association in one family. 
And this general structure is very unlike that of the supposedly 
tarsioid genera, such as Tetonius or Necrolemur, with which there is. 
equal or greater reason for supposing Paromomys to be related. 

To propose as a tentative solution of this extraordinarily intricate- 
problem that Paromomys is a derivative of a tarsioid-notharctine- 
ancestry is not fully satisfactory, for a corollary would be that the- 
Notharctinae were descended from a different tarsioid or pro to tarsioid 
ancestry from the Adapinae, one with more Paromomys-like molars- 
and this is wholly unsatisfactory on the basis of the mutual relations 
of Notharctinae and Adapinae as inferred from their own much, 
better known structures. It is much more probable either that the 
marked resemblance in the molars of Paromomys and Pelycodus i& 
wholly convergent or that Paromomys is really a divergent offshoot 
of the earliest notharctine ancestry toward wiiich various tarsioids- 
have converged in one way or another. The second alternative would 
imply extreme antiquity of the Pelycodus pattern and the very remote- 
separation of Notharctinae and Adapinae, to a degree that seem& 
improbable. The very tarsioid, and not particularly Pelycodus-like^ 
pattern of Palenochtha, which nevertheless seems almost surely to be- 
a fairly close relative of Paromomys and Palaechthon, and the many 
distinctly tarsioid characters of the latter genera, however electic in 
their combination, also suggest that the former alternative is more- 
probable, as Gidley concluded. I must confess, however, that I see- 
no way of forming a really strong and reasonable opinion on this, 
problem from the present evidence. 

Genus PAROMOMYS Gidley 

Paromomys Gidley, 1923, p. 3. 

Type. — P. maturus Gidley, 1923. 

Distribution. — Middle Paleocene, Fort Union, Mont. 

Diagnosis. — Dental formula probably tjM- Lower incisor enlarged ;>, 
root extending beneath P2. Canine normal or slightly reduced^ 
P2 present, 2-rooted. P4 not enlarged, paraconid and metaconid 
very rudimentary or absent, trigonid apex slightly higher than Mr^ 
iieel low, bicuspid. Molars with short trigonids, with closed, small^. 



FORT UNIOJ^ OF CRAZY MOUNTAIN FIELD, MONT. 149^ 

quadrangular, transverse trigonid basins, paraconids small and 
closely approximated to metaconids, especially on M2-3; cusps. sub- 
marginal; no metastylid. Talonid of M3 greatly enlarged, with strong- 
third lobe with (at least) tv/o distinct, transversely paired cusps. 
P^ 2-rooted. P* 3-rooted, with strong protocone, no distinct meta- 
cone. Upper molars primitively tritubercular, \\dthout mesostyle, 
protostyle, or hypocone, but with a ridge from the protocone swinging 
around the posterointernal corner, which is much expanded and 
basined. Internal bases generally bilobed. 

The morphology of the genus is described under its type species, 
and the distinctive characters of the second species mentioned under it. 

PAROMOMYS MATURUS Gidley 

Figures 30, 31; Plate 7, Figures 2, 2a, 3, 3a; Plate 8, Figures 2, 2a, 3, 3a 
Paromomys maturus Gidley, 1923, p. 3. 

Type. — U.S.N.M. no. 9473, right lower jaw with P4-M3 and anterior 
alveoli. Collected by A. C. Silberling. 

Horizon and locality. — All known specimens from Gidley Quarry, 
Fort Union, Middle Paleocene horizon. Crazy Mountain Field, Mont. 

Diagnosis. — Trigonids Mi -2 notably narrower than talonids. P* 
strongly transverse. Internal bases of M^~^ strongly bilobed. Meas- 
urements and derived statistical data given below. Dental formula 
nM (but see below). All teeth closely placed, vidthout diastema. 

Discussion.— Theie are six specimens in which the anterior alveoli 
are all shown, although in none are their rims unbroken. One of 
these, as noted by Gidley (1923, p. 9 — Gidley mentions two, but the 
other is not of this species), has a minute pit external to and between 
the incisor and canine, which might be an alveolus for a vestigial 
incisor. It could, however, be a mere break, and as none of the other 
five specimens shows it this is a more probable explanation. I2 was 
thus probably absent, and if ever present was vestigial and oftener 
lacking. 

The incisor and canine are unknown except by their alveoli. The 
incisor was large, its root slightly compressed laterally, and was semi- 
procumbent, its root extending to beneath the posterior end of P2 
or anterior end of P3. The canine was considerably smaller, its nearly 
circular root with about half the (maximum) diameter of Ii. It is less 
procumbent, and its root is shorter than that of Ii, the root of which 
passes beneath it. The one canine root occupies about the same 
space as the two of P2. 

P2 has two separated, divergent roots. The crown is high, slender, 
very slightly procumbent, and somewhat recurved at the tip. The outer 
face is convex, the inner excavated anteriorly and posteriorly, adjacent 
to curving, vertical sharp anterointernal and posteroexternal crests.. 



150 



BULLETIN 16 9, UNITKD STATES NATIONAL MUSEUM 



On one specimen (9479) there is a very minute anterior cuspule, high 
on the crown, which is only very vaguely suggested on a second speci- 
men surely of the same species (9676). There is a low and very 
small heel, with a minute cusp at the posteroexternal corner of the 




Figure 30.—Paromomys maturus Gidley, U.S.N.M. no. 9473, right lower jaw: a, Crown view; 6, internal 
view. Four times natural size. (After Gidley, 1923, flg. 1.) 




Figure Zl.—Paromomys matmus Gidley, U.S.N.M. no. 9540, left upper jaw: a, Crown view; 6, external 
view. Four times natural size. (After Gidley, 1923, fig. 2.) 



tooth, at the base of the posterior crest, from which a ridge passes 
downward and internallj^ to the posterointernal corner. 

P3 has about the same length and height as P2 but is considerably 
wider and more robust. The anterior crest is median near the apex 
and turns inward below this, an accentuation of the slighter curve of 



FORT UNIOJs^ OF CRAZY MOUNTAIN FIELD, MONT. 151 

this crest on P2. The posterior crest is less curved and is only slightly 
external to the midline, the tooth being much more swollen external 
to it than is Po. The heel is more definite, much wider, the cusp less 
external, and the ridge less sloping. 

P4 is much longer and wider and somewhat higher than P2, shorter, 
slightly narrower and somewhat higher than Mi. Aside from its 
greater size, it differs from P3 chiefly in the much stronger heel. A 
small cusp appears at the posterointernal angle, and a ridge running 
anteriorly from this tends to close a small basin. A minute cuspule 
may appear about halfway up the crown on the inside of the anterior 
edge, but this rudiment is often lacking even on unworn teeth. Simi- 
larly, a very vague rudiment of a metaconid appears on the most 
progressive variants (e. g., 9545) but is oftener absent. 

The molars have small trigonids and large basined heels. On Mi 
the trigonid is well elevated and is du'ected somewhat forward, while 
on M2_3 it is progressively lower. On Mi_2 the talonid is considerably 
wider than the trigonid, the inner face of the tooth base being along 
a straight anteroposterior line and the outer face strongly oblique. 
On M3 the trigonid and anterior half of the talonid are of about equal 
width. The enamel is nearly smooth, but on completely unworn 
teeth the basin is somewhat wrinkled. Variable, crenulated external 
cingula are developed on all the molars except on the third lobe of 
M3. There are no internal cingula. 

The paraconid is present on all the molars and is anterior and 
slightly external to the metaconid. On Mi it is definite and well 
separated from the metaconid, although small. On M2-3 it is much 
closer to the metaconid and is almost fused with the latter, disappearing 
with slight wear. On Mi the metaconid is about equal to the proto- 
conid, and on M2-3 it is higher. On all, the metaconid is internal and 
slightly posterior to the protoconid, and the two are connected by a 
notched crest. Another, less prominent crest runs forward and slight- 
ly inward from the tip of the protoconid to the anteroexternal angle 
of the tooth, then internally along the anterior rim to the paraconid, 
enclosing a short, transverse, very shallow and small trigonid basin. 

Mi_2 have typical hypoconid and entoconid of about equal height. 
The sharp basin rim is vaguely expanded in the hypoconulid region, 
but no definite apex is here formed. There are no metastylids. 

The heel of M3 is very elongate, with two definite lobes each pri- 
marily with two large cusps, one external and one internal. The pos- 
terior, or hypoconulid, lobe may be further complicated by the incipi- 
ent fission of one or both of its cusps, and adventitious cuspules may 
even appear in the basin, the exact structure of this part being highly 
variable, although its basic features, the extension of the basin into a 
third lobe and the strongly double hypoconulid, are constant. 

119212—37 11 



152 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

The symphysis is short, unfused, and relatively deep. There is a 
larger mental foramen beneath P2 or the posterior part of the canine 
and another, smaller, beneath P4. The dental foramen was far back 
of the molars and slightly below the alveolar level. The angular 
process is not completely preserved in any case but was directed 
decidedly downward, as well as backward, and evidently was strong 
and more or less styliform. Condyle and coronoid are not preserved. 

The upper canine is represented only by part of its alveolus in one 
specimen (9540). This suggests that it was strongly reduced, the 
portion of alveolus preserved indicating a root not larger than the pos- 
terior root of P-. P^~^ are known only from alveoli. Each had a 
small anterior and large posterior root. On P^ the disparity is greater, 
and the posterior root more transverse, but even it apparently does not 
have a third root, and the inner heel, or protocone, must have been 
small. 

P* is a large, transverse tooth with three separate roots. The high 
outer cusp, paracone or amphicone, is vaguely triangular and is 
single, only very slight inner and outer vertical depressions suggesting 
the incipient appearance of a metacone on its posterior slope. There 
is a small, distinct parastyle and a much less distinct metastyle higher 
on the crown than the parastyle. The posterior half of the outer face 
has a narrow, sharp basal cingulum. The protocone is large and 
definite but lower than the amphicone, and its apex is anterior to a 
median transverse line across the tooth. From it a small sharp, 
cingular crest runs to the parastyle. Another crest falls away directly 
posteriorly from its apex to the expanded posterointernal angle of the 
crown, where it turns nearly at right angles and becomes a well- 
developed but simple posterior cingulum. A minute, isolated cuspule 
appears in the position of a metaconule. 

M^ and jSP are almost identical in structure, differing only in outline 
and proportions. Paracone and metacone are strong, distinct, and 
nearly equal, the paracone very slightly larger. There is a strong 
external cingulum, rising at the anteroexternal comer without definitely 
forming a parastyle cusp. The metastyle is likewise small and vague 
but is more nearly cuspidate. There is no trace of a mesostyle. The 
inner face of the tooth is flattened and has a distinct, median, vertical 
groove that divides it into two basal lobes, the posterior lobe being on 
M' slightly and on M^ distinctly larger. These lobes, however, do not 
correspond to distinct cusps. There is only one cusp, the protocone, 
which is on the posterior lobe very near the distal end of the groove. 
Although larger, the protocone has the same structure as on P* with 
the addition of a ridge to the metaconule, departing not from the 
apex but from the posteroexternal slope. The anteroexternal ridge, 
as on P^, runs to the anteroexternal comer, or to the parastyle (here 
less distinct) but at its midpoint here has a cuspule, a protoconule, the 



FORT UKIOX OF CRAZY MOUXTAIX FIELD, MONT. 



153 



posteroexternal base of which also meets a small ridge descending the 
inner face of the paracone. This protoconule is very small, and the 
metaconule is still smaller and indistinct. The posterior crest from 
the protocone apex forms a sharp loop around the expanded posteroin- 
ternal corner of the crown, thus maldng the teeth distinctly quadrate 
although no hypocone is present. 

^P is shorter than M^~^, with the whole posterior half, most notice- 
ably the metacone and posterointernal loop, much reduced. The 
internal base has only one lobe. On one specimen (9542) there is no 
groove, and on the other (9540) it is very slight and does not reach the 
base. 

Table 30. — Numerical data on lower teeth of Paromomys maturus 



Variate 


N 


R 


M 


(T 


V 


LP4 

WP4 

LMi 


18 
18 
21 
21 
20 
20 
14 
17 
13 
19 
10 


2. 3-2. 8 
1.6-1.9 
2. 8-3. 2 
2. 0-2. 3 
2. 9-3. 2 

2. 2-2. 5 

3. 3-3.8 
1. S-2. 1 

0. 77-0. 89 

1. 25-1.41 
1. 16-1. 31 


2. 556 ±0. 026 

1. 778 ±0.022 

3. 005 ±0.020 

2. 233 ±0.018 

3. 040 ±0.024 

2. 355 ±0.017 

3. 59 ±0.03 
1. 994 ±0.006 
0.837 ±0.009 
1. 298 ±0.011 
1. 215±0. 014 


0. 112±0. 019 
0. 092 ±0. 015 
0. 090±0. 014 
0. 084 ±0. 013 
0. 108 ±0. 017 
0. 074 ±0.012 
0. 130 ±0. 025 
0. 025 ±0. 004 
0. 034 ±0. 007 
0.046 ±0.007 
0. 046 ±0.010 


4. 4±0. 7 

5. 2±0. 9 
3. ± 0. 5 


WMi 

LM2 - 


3. 8±0. 6 
3. 5 ± 0, 6 


WM2 

LM3 

WM3 

LP4:LMi 

LM2:WM2-.. 
LM3:LM2 


3. 1 ± 0. 5 
3. 6±0. 7 
1. 3±0. 2 



Table 31. — Measurements of individual specimens of Paromomys maturus 

Type Lower Jaw i 



Fa 


M: 


Mj 


Mj 


M,-} 


LP4 

LMi 


LM2 
WM2 


LMs 


L 


W 


L 


w 


L 


w 


L 


w 


LMj 


Mm 
2.5 


Mm 
1.7 


Mm 


Mm 
2.2 


Mm 
3.1 


Mm 
2. ,3 


Mm 
3.6 


Mm 

1.9 9.0 


0.81 


1.35 


1.16 



Characteristic Upper Dentitions 



U.S.N.M.no. 


P< 


Ml 


M2 


M3 


Mi-3 


LP< 
LM' 


WM2 
LM> 


LM» 




L 


W 


L 


W 


L 


W 


L 


W 


LM3 


9540 

9542 


Mm 
2.9 
2.5 


Mm 
3.4 
3.0 


Mm 
2.9 
2.6 


Mm 
4.0 
3.8 


Mm 
2.9 
2.6 


Mm 
4.1 
4.0 


Mm 
2.3 
2.0 


Mm 
4. 1 
3.6 


8.3 

7.4 


1.00 
0.96 


1.41 

1.54 


0.79 
0.77 







1 These measurements have been taken, and ratios calculated, on 30 difierent specimens, but these are most 
usefully summed up by the statistical data derived from them and wherever possible in this memoir I do not 
publish the long tables of raw measurements. Data for M1-3 have not been calculated. Althouirh at first 
sight this would appear to be the best single size measurement, in fact it depends to so great a degree on 
crushing and other extraneous factors as to be highly inaccurate and hence of little value. 



151 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

The infraorbital foramen is high and narrow and lies immediately 
anterior to the anterior root of P*. Very little of the orbital rim is 
preserved, and I see no basis for supposing it larger or smaller than in 
any possibly related group. It seems probable that it extended little, 
if any, farther forward than P*. 

The principal numerical data on lower teeth of this species are given 
in table 30 (see also fig. 3). 

The highly homogeneous character of the sample, and by inference 
the only slightly variable nature of the species, is very striking. All 
the coefficients of variation are remarkably low and even the highest, 
5.16 ±0.86, is very commonly exceeded in races that are pure in the 
strictest sense. 

There are too few upper jaws to calculate derived statistical data. 

PAJROMOMYS DEPRESSIDENS Gidley 

Figure 32; Plate 9, Figure 7 
Paromomys depressidens Gidley, 1923, p. 4." 

Type. — U.S.N.M. no. 9546, part of right upper jaw with P^-A'P. 
Collected by A. C. Silberling. 

Horizon and locality. — All known specimens from Gidley Quarry, 
Fort Union, Middle Paleocene horizon. Crazy Mountain Field, Mont. 




Figure Z2.— Paromomys depressidens Gidley, U.S.N.M. no. 9485, left lower jaw, crown view. Four times 
natural size. (After Gidley, 1923, fig. 3.) 

Diagnosis. — Trigonids of Mi_2 nearly as wide as talonids. P^ less 
transverse than in P. maturus. Bases of M^~^ less strongly bilobed. 
Size notably smaller; length M2 (mean of three specimens), negative 
deviation from mean in P. maturus about eight times standard devia- 
tion of latter. See also measurements in table 33. P4 larger relative 
to Mi; ratio LP4:LMi (one specimen), positive deviation from mean 
in P. maturus over three times standard deviation of latter. M2 wider 
relative to its length; ratio LM2:WM2 (mean of three specimens), 
negative deviation from mean in P. maturus nearly three times stand- 
ard deviation of latter. 

Discussion. — Ii-Ps are loiown only from their alveoli, which are 
developed about as in Paromomys maturus. Of the two specimens 
showing these alveoli, one (9416) has a possible alveolus for a vestigial 
I2, and the other (9482) does not, so that, as in P. maturus, this tooth 
was either absent or inconstant. P4 is slenderer and somewhat less 

6< In referring to Gidley's description, note that the text has been transposed. The text in Gidley, 1923, 
from p. 5, line 12, beginning "Several upper -jaw portions . . ." to p. 6, line 3, ending ". . . above the junc- 
tion of P3 and P'" is made part of the description of P. depressidens but in fact refers to P. maturus and evi- 
dently was meant to follow p. 4, line 12, of text, after ". . . as in Notharctus nunienus (Cope)." 



FORT UNIOX OF CRAZY MOUNTAIN FIELD, MONT. 



155 



progressive than in P. maturus, being to some extent intermediate in 
structure between P3 and P4 of that species. The supposed depression 
of the molar trigonids, stressed by Gidley, involves slight differences 
that defy accurate measurement. To my eye they do not appear at 
all less elevated than in P. maturus. The trigonids of M2_3 are rela- 
tively slightly shorter, and the paraconids may be still more nearly 
connate with the metaconids. More definite is the fact that on M2 the 
trigonid is nearly as wide as the talonid, while in P. maturus it is 
definitely narrower. Perhaps in keeping with the smaller size, the 
heel of M3 is rather simple, and although it has the basic structure of 
P. maturus in some variants the third lobe is less wide and its two main 
cusps less distinct. 

The available upper teeth of this species are all deeply worn, and I 
believe that the characters given by Gidley, "cusps and lophs depressed 
and basins shallow; protoconules present but less well defined than 
P. maturus; metaconules absent", are all due to this wear, or at least 
that the wear makes it impossible to know whether these are true 
morphological characters or not. P* is much less transverse than in 
P. maturus, and the inner sides of the bases of M^~^ are less strongly 
bilobed. Otherwise the structure seems to be very similar, as far as it 
can be surely determined. 

The species is decisively distinct from the genotype, and there can 
be no question as to its validity in spite of the fact that P. maturus and 
P. depressidens were absolutely contemporaneous and both are known 
only from the same very limited locality. These facts and the very 

Table 32. — Measurements of known specimens of Paromomys depressidens 

Lower Jaws 



U.S.N.M.no. 


P4 


Ml 


M2 


Ms 


Ml-3 


LP4 


LM2 
WM2 


LMs 


L 


W 


L 


W 


L 


W 


L 


W 


LMi 


LMj 


S485 


Mm 


Mm 


Mm 
2.0 
2.0 


Mm 
1.6 


Mm 
2.0 


Mm 
1.8 


Mm 
2.6 
2.8 
2.7 


Mm 
1.5 
1.6 
1.6 


7.0 
6.9 


0.95 


1.11 

1.22 
1.21 


1 30 


9677 


1.9 


1.2 




9482.- 




2.2 
2.3 


1.8 
1.9 


1 23 


9416 


1.8 


1.2 





























Upper Jaws 



U.S.N. M. no. 


P< 


Ml 


M2 


M3 


M'-3 


LP4 

LM' 


WM2 
LM2 


LM3 


L 


W 


L 


W 


L 


W 


L 


W 


LM» 


9546 


Mm 
1.9 


Mm 
2.0 


Mm 
2.0 
2.1 


M7n 
2.6 
2.5 


Mm 
2.0 
1.9 

2.1 


Mm 
3.0 
2.8 
3.3 


Mm 
1.5 
1.3 
1.5 


Aim 
2.7 
2.2 
2.7 


5.7 


0.95 


1.50 
1.47 
1.57 


75 


9548 


0.68 


9549 










0.71 



















156 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

marked specific distinction suggest that complete, unworn dentitions 
might prove generic distinction, but the material actually in hand does 
not warrant such a conclusion. 

As the samples are small, measurements of all known specimens are 
given in table 32 (see also fig. 3). 

Genus and Species Undetermined 
Cf. PAHOMOMYS 

In 1932 Silberling and I found at Loc. 13 a single left AP, apparently 
representing an otherwise unknown primate. It resembles Plesiadapis 
anceps but not very exactly and is still less like other species of that 
genus. It is probably too small to belong to Plesiadapis rex, which 
occurs at the same locality. It resembles Paromomys maturus more 
closely than any other species with which comparison has been made, 
but it is more transverse, has the inner face even longer and more 
sloping, and has the anterointernal, not posterointernal, basal part 
definitely more projecting. It also resembles the most primitive 
species of Pelycodus but could not belong in that genus. Such an 
isolated tooth is inadequate for generic, or even for certain family 
identification, but its presence seems worth recording. 

Genus PALAECHTHON Gidley 

Palaechthon Gidley, 1923, p. 6. 

Type. — P. alticuspis Gidley. 

Distribution. — Middle Paleocene, Fort Union, Montana. 

Diagnosis. — Dental formula probably \' l 3 | . Lower incisor and 
canine about as in Paromomys, or possibly incisor slightly larger and 
canine slightly smaller. Roots of P2 less divergent or incompletely 
divided. P4 larger relative to Mi, taionid as in Paromomys, but 
trigonid with distinct, subequal paraconid and metaconid. Alolar 
trigonids very similar to Paromomys but on M2_3 paraconid slightly 
more distinct, lower on the crown, and less marginal. M3 wdth double 
hypoconulid, but third lobe less strong than in Paromomys. Trigo- 
nids more elevated. Upper molars somewhat more transverse than 
in Paromomys maturus, internal bases less distinctly bilobed, and 
posterointernal expansion less marked. 

PALAECHTHON ALTICUSPIS Gidley 

Plate 7, Figure 1 ; Plate 9, Figures 5, 6 

Palaechthon alticuspis Gidley, 1923, p. G. 

Type.— U.S. N.M. no. 9532, right lower jaw with P2-M2. Collected 
by A. C. Silberling. 



rORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 157 

Horizon and locality. — All known specimens from Gidley Quarry, 
Fort Union, Middle Paleocene horizon. Crazy Mountain Field, Mont. 

Diagnosis. — Sole known species of genus as redefined. See mor- 
phological and numerical data (table 33). 

Discussion. — From their alveoli, in two specimens (9532 and 9534), 
Ii and C are much as in Paromomys maturus, but the incisor is perhaps 
relatively a little larger and the canine still smaller, its alveolus 
occupying distinctly less space than the alveoli of Po. There is no 
evidence of a second incisor. 

The alveoli of P2 are confluent, and in one specimen the roots are 
fused, in another barely separate. P2 and P3 are similar to each other 
and to those of P. maturus. P2 is slenderer and slightly higher than P3 
and P3 has the incipient anterior cuspule more nearly distinct than Po. 

P4 is much more progressive than in Paromomys, having small but 
distinct subequal paraconid and metaconid in all cases, whereas in 
Paromomys these cusps are either barely incipient or entirely absent 
on P4. The talonid and general structure are, however, as in Paro- 
momys. 

Ml almost exactly resembles that of P. maturus. M2-3 are also 
closely similar but have the paraconid more distinct than is usual in 
Paromomys, lower on the crown and also a little more external, or less 
marginal. On both Mi and M2 the trigonid is nearly as wide as the 
talonid. On Mi_3 the trigonid is more elevated than in Paromomys, 
and the external cingulum is weak or absent on the talonid. The third 
lobe of M3 is much less developed than in Paromomys maturus, but 
the hypoconulid is bifid or, in one case (9430) approximately trifid. 

The mandible is also much as in Paromomys. In one specimen 
(9450) most of the posterior part is present, although the ends of the 
three processes are broken. The inner face is nearly plane. The 
coronoid is broad and apparently rose little above the articular process. 
Its anterior border is nearly straight and at right angle to the alveolar 
border. The condyle is far above the molar level. The large dental 
foramen is far posterior to the teeth, beneath the corono-condylar 
notch, and is above the alveolar level. The angle is long, slender, 
styliform, and thickened, and extends backward and slightly down- 
ward. Its tip was posterior to a vertical from the condyle. 

P* is not known, but it has three roots and was nearly as wide as M^ 
The upper molars closely resemble those of Paromomys maturus 
except in being somewhat more transverse, with slenderer sharply 
pointed cusps, and in the much less marked posterointernal expansion 
and basining. There is an internal vertical groove, but on M' the 
base is not bilobed and on M^ this is barely indicated. Several of 
these points are resemblances to Paromomys depressidens, and it has 
already been noted that the teeth on which that species is based are 
much worn and of doubtful detail. As the two species are of about 



158 



BULLETIN 16 9, UNITED STATES NATION.\L MUSEUM 



the same size, the status of these upper jaws is dubious, although the 
lower jaws are quite distinct, and it is unfortunate that one type is 
an upper jaw and the other a lower. The upper jaws are, however, 
probably distinct and correctly associated with the lower jaws as 
determined by Gidley. Those placed in Palaechthon alticuspis are 
very slightly smaller, molars definitely more transverse, and the pos- 
terointernal basin probably less developed. It seems justifiable, in 
the absence of definite evidence to the contrary, to accept the identi- 
fications established and thus avoid changing the nomenclature, con- 
sidering the separation of the species and genera as validated by the 
lower jaws and, for the present, overlooking the fact that one type is, 
in fact, an upper jaw and of doubtful status. 

Table 33. — Numerical data on Palaechthon alticuspis 



Variate 


N 


LM, 


10 


WM. 


9 


LMz 


12 


WM2 


11 


LMsiWMs--. 


11 



R 



1. 9 -2. 1 
1. 5 -1. 7 
1. 9 -2. 2 
1. 5 -I. 8 
1. 17-1. 40 



M 



2. 030 ±0. 025 
L 567 ±0. 022 
2. 067 ±0. 024 
1. 682 ±0. 025 
1. 231 ±0. 021 



0. 078 ±0. 017 
0. 066 ±0. 016 
0. 085 ±0. 017 
0. 084 ±0. 018 
0. 070 ±0. 015 



3. 8±0. 9 

4. 2±L 

4. 1±0. 8 

5. Oil. 1 



Table 34. — Individual measurements of Palaechthon alticuspis 
Typk and Characteristic Lower Jaws 



U.S.N.M. no. 


P4 


Ml 


M2 


M3 


Ml-3 


LP4 

LMi 


LM2 
WMs 


LM3 


L 


W 


L 


W 


L 


W 


L 


W 


LMi 


9532 


Mm 
1.9 
2.1 
2.0 


Mm 
1.2 
1.2 
1.2 


Mm 
L9 
2.1 
2.1 


Mm 
1.5 
1.6 

1.5 


Mm 
2.0 
2.1 
2.1 


A/TO 

1.7 
1.7 
1.6 


Mm 


Mm 




1.00 
1.00 
0.95 


1.18 
1.24 
1.31 




9430 

9483 


2.4 
2.3 


1.3 
1.4 


6.5 
6.3 


1.14 
1.09 



Upper Jaws (only two are known) 



U.S.N.M. no. 


Ml 


M2 


M3 


Mi-3 


WM2 
LM2 


LM3 


L 


W 


L 


W 


L 


W 


LMa 


9550 


Mm 
1.9 
1.9 


Mm 
3.0 
3.0 


Mm 
1.7 
1.9 


Mm 
3.0 
3.2 


Mm 
1.3 


Mm 
2.5 


5.3 


L76 
1.68 


0.76 


9551 















Genus PALENOCHTHA Simpson 

a lenochtha Simpson, 1935d, p. 231. 

Type. — Palaechthon minor Gidley. 

Distribution. — Middle Paleocene, Fort Union, Montana. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 159 

Diagnosis. — Dental formula probably H^^. Anterior lower denti- 
tion shorter than in Paromomys or Palaechthon and apparently with 
one tooth absent, probably P2. P4 of about the same length relative 
to Ml as in Palaechthon alticuspis but relatively higher, with no sign of 
the metaconid and only vague rudiment of the paraconid. M1-2 
similar to those of Palaechthon, but M3 with smaller third lobe and 
single hypoconulid. Upper molars similar to those of Paromomys 
and Palaechthon but very slender, transverse, and more triangular. 
Posterointernal expansion weak. Inner base not bilobed. M^ 
shorter relative to M^. 

Discussion. — In describing Palaechthon minor, Gidley (1923, p. 8) 
said: "Most of the differences noted above suggest for the species just 
described a slightly different line, or direction, of development than is 
indicated in P. alticuspis. It is possible, therefore, that more complete 
materials may prove that these two species do not form a natural 
generic group." Although more complete materials are still lacking, 
I do not see how this species can be placed in Palaechthon. The 
further reduction of the anterior teeth, the absence of a metaconid and 
of a distinct paraconid on P4 (not explicitly mentioned by Gidley), 
and the single hypoconulid on M3 are just such differences as are used 
to distinguish genera among all early primates. While it is true, as 
Gidley notes, that the upper molars differ less from Palaechthon 
alticuspis than do the lowers, still the differences are rather more 
marked than are those between the latter species and Paromomys 
depressidens . Unfortunately, the anterior upper teeth, which often 
show more marked generic characters, are unknown, but I think there 
can be no doubt that the genus is distinct. 

PALENOCHTHA MINOR (Gidley) 

Figure 33; Plate 10, Figure 1 
Palaechthon minor Gidley, 1923, p. 7. 

T^/pe.— U.S.N.M. no. 9639, right lower jaw wdth P4-M3 and anterior 
alveoli. Collected by A. C. Silberling. 

Horizon and locality. — All known specimens from Gidley Quarry, 
Fort Union, Middle Paleocene horizon, Crazy Mountain Field, Mont. 

Diagnosis. — Sole known species of the genus as described above. 
See description below and measurements in table 35. 

Discussion. — Teeth anterior to P4 are represented only by alveoli 
in the type and in no. 9631. Both show an alveolus for a large, some- 
what compressed, procumbent incisor, followed by a smaller, more 
erect alveolus, evidently for a canine. Between this and P4 there 
appears to be only a small double alveolus, or two very small alveoli 
confluent at their mouths. It is higlily probable that this lodged one 
tooth, P3, and in this event P1-2 must have been missing. There 



160 



BULLETIN 169, UNITED STATES NATIONAL MUSEUM 




appears, however, to be no diastema, and the antemolar region of the 
jaw is relatively shorter than in the other genera here considered, what- 
ever may have been the exact number and homologies of the teeth. 

P4 is relatively higher, slenderer, and simpler than in Palaechthon. 
In the two available specimens there is no clear trace of a metaconid, 
and the paraconid is represented only by a very rudimentary and 
scarcely visible angulation of the anterior edge. The heel is short but 
is relatively broad and has a rudimentary basin and two very small 
and poorly differentiated posterior cuspules. 

Mi_2 are almost identical in structure with those 
of Palaechthon. The trigonid of M3 is also closely 
similar, but the talonid is different. It is reduced, 
more pointed posteriorly, with the third lobe de- 
cidedly narrower and less clearly differentiated, and 
the h3q30conulid apparently single. 

In the upper dentition, only M^~^ are now known. 
These are basically similar to those of Palaechthon 
but give quite a different superficial impression by 
reason of their more delicate structure, more transverse and triangular 
outhne, and the accentuated forward twist of the protocone, present 
in the other primate genera but here most strongly developed. Para- 
style and metastyle are distinct and subequal, as are protoconuie 
and metaconule. The inner face of the protocone is flattened and 
bears a faint vertical depression, but the base is not at all bilobed. The 
posterointernal basin or expansion is only faintly indicated, less de- 
veloped than in the other genera. M^ is short, rather strongly tri- 
angular, and developed analogously to that of Palaechthon. 



Figure ZZ.—Paienochtha 
7wino)-(Gidley),U.S,N.M, 
no. 9590, left upper mo- 
lars, crown view. Four 
times natural size. (After 
Gidley, 1923, fig. 4.) 



Table 35. — Individual measurements of Palenochtha minor 
Type and Principal Referred Lower Jaws 



U.S.N.M.no. 


P4 


Ml 


Ms 


Ms 


M,_3 


LP4 

LMi 


LMj 

WM2 


LMs 


L 


w 


L 


W 


L 


W 


L 


W 


LMs 


9639... 


Mm 
1.3 
1.1 


Mm 
0.8 
0.7 


Mm 
1.3 
1.2 
1.3 


Mm 
1.1 
1.0 
1.0 


Mm 
1.3 
1.3 
1.3 


Mm 
1.2 
1.0 
1.1 


Mm 
1.5 


Mm 
0.9 


4.3 


1.00 
0.92 


1.08 
1.30 
1.18 


1.15 


9631 




9636 


1.4 


0.9 


4.3 


1.08 











Upper Jaws (all known) 



U.S.N.M. no. 


Ml 


M!> 


M3 


Mi-3 


WM2 
LMJ 


LM» 


L 


W 


L 


W 


L 


W 


LM » 


9590 


Mm 
1.3 


Mm 
2.0 


Mm 
1.2 
1.4 


Mm 
2.0 
2.0 


Mm 
0.8 


Mm 
1.6 


3.8 


1.67 
1.43 


0.67 


9595 



















rORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 161 

Family CARPOLESTIDAE Simpson, 1935 

As was pointed out in describing Carpolestes (Simpson, 1928, p. 
10), Elphidotarsius supplies a good morphological ancestry for the 
very peculiar and aberrant genera Carpodaptes Granger and Matthew 
of the Tiffany and Carpolestes Simpson from Tiffany or slightly later 
equivalents in the Fort Union. The present opportunity to compare 
the genotypes of the three genera at first hand fully confirms this and 
leaves no doubt that they are closely related. 

Elphidotarsius and Carpolestes show the same highly characteristic 
basic structure throughout P4-M3. Carpodaptes has P4 more enlarged 
than in Elphidotarsius, its apical cuspules all in a straight line and one 
more in number. On Mi the trigonid is still more elongate, and the 
paraconid almost directly anterior to the protoconid. Oth^er struc- 
tural distinctions are very slight and unimportant. In Carpolestes P4 
is still larger, its cuspules increased to seven or eight, its heel elevated 
to the trigonid level of Mj. On Mi the paraconid and protoconid are 
exactly in the same longitudinal line and continue without a break 
the cuspule series of P4. The structural sequence Elphidotarsius- 
Carpodaptes-Carpolestes is almost perfect (also in the size of the 
known species) and may be a direct phylogeny, although the possible 
age difference between the last two genera seems too small to permit 
such a marked structural advance in a direct descendant, and it is 
more likely that some collateral evolution is involved. 

Upper teeth are as yet known only in the genera Carpolestes (Car- 
polestes dubius Jepsen; see Jepsen, 1930a) and Carpodaptes. The 
molars are of primitive tritubercular type, with distinct hypocone, 
more or less closely paralleled in some primitive Eocene primates 
(e. g., Omomys, Caenopithecus, Pseudoloris, and others). P^~*, how- 
ever, are very extraordinary and unlike anything known in any other 
primate or indeed any placental mammal, to such a degree that when 
the first isolated example of one of these teeth was found I hesitantly 
referred it to the Multituberculata {" Lifotherium" ®^ Simpson, 1929, 
p. 9), and this remarkably bad guess was onlj?^ corrected when Jepsen 
found associated premolars and molars. Like the last premolar of 
Ptilodus, both P^ and P* have tliree longitudinal rows of cusps. 

These premolars are much unlike those of any tarsioid, as is P4, but 
it may confidently be predicted that P^-* of Elphidotarsius, when 
found, will distinctly approach the normal tarsioid type, as does P4 
of that genus. P ^~* of Carpodapttes are indeed closer to Carpolestes, 
but they show some approach to more norm^al structure. 



«» A strict synonym of Carpoteslcs Simpson, 1928. The retention of Carpolestes as the definitive name is 
not only preferable, as Jepsen suggests, but also the only possible course in accordance with the rules of 
nomenclature. 



162 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

The dental formula is also most completely known in Carjwlestes 
duhius, in which it is tjxIj^^ ^s in Paromomys. The incisor is en- 
larged but does not extend beneath P4, also as in Paromomys, but the 
canine is more reduced. In both Carpolestes and Carpodaptes P2-3 
are reduced to 1 -rooted vestiges with buttonlike crowns. 

Noting these divergent specializations, bat also the strong hint of 
tarsioidlike upper molars, in the most specialized genus of the phylum 
in characters not known in Elphidotarsius, we may expect the latter 
to cast more light on affinities as far as its more scanty remains go. 
P4 in this genus could easily be derived from one like that of, say, 
Palaechthon, but it is already too specialized, and its structural ancestor 
must have been too generalized, to cast any real light on affinities. 
Ml also shows what may be taken as the beginning of a narrowly 
phyletic specialization in its elongate trigonid. Otherwise it is much 
like that of many tarsioids but of too generalized a heritage to give 
decisive evidence. M2-3 are almost exactly like those of Pronothodedes , 
so much so that were this form known from those teeth alone it would 
have to be defined as a species of Pronothodectes. They also resemble 
to a marked degree those of Eocene primates of other groups, such 
as Wmomys vespertinus and, in less degree, Pelycodus. As far as I know 
they do not so closely resemble any genus not now considered as 
primate. The characters that are distinctive from the most generalized 
tuberculosectorial pattern and that are not clearly habitus characters 
or otherwise neomorphs of this very restricted phylum all appear to 
me to be definitely primate. To tliis extent I cannot agree with Jepsen 
(1930a, p. 523 — he was, however, dealing only with the much more 
aberrant terminal genus Carpolestes and had not recognized the 
relationship to Elphidotarsius) that "it is possible to select suites of 
characters which, taken by themselves, would place Carpolestes in any 
one of several orders." I do, of course, recognize that a really defini- 
tive determination of affinities is in such cases practically impossible 
from teeth alone, but since teeth are, in fact, all we have I see no 
useful alternative to classifying them at least tentatively as belonging 
to the group they most resemble, that is, to the Primates. 

The family in wliich these related, aberrant animals are placed was 
defined and discussed in revising the Tift'any fauna (Simpson, 1935c). 

Genus ELPHIDOTARSIUS Gidley 

Elphidotarsius Gidley, 1923, p. 10. 

Type. — E. florencae Gidley. 

Distribution. — Middle Paleocene, Fort Union, Montana. 
Diagnosis. — Three lower molars and at least one premolar, dental 
formula otherwise unknown. P4 enlarged, equaling or exceeding Mi in 

6' Jepsen writes 1.0.4.3. It is, of course, Impossible to say which is correct, but the form I give seems to 
me slightly more probable, and it facilitates comparison by being consistent with the other formulae hero 
used. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 163 

every dimension. Apex with four cuspules, second highest, first three 
anteroposterior, and fourth shghtly internah Talonid very short, 
with one cusp. Mi with elongate trigonid, paraconid far from meta- 
conid, no trigonid basin. IMo-s with closed trigonid basins and para- 
conid small, near metaconid, but distinct. Talonid of M3 with well- 
differentiated third lobe, posterointernal rim elevated and vaguely 
including two or more apices. Protoconid reduced on M2_3. Trigonid 
cusps all well in from the margin. 

ELPHIDOTARSIUS FLORENCAE Gidley 

Plate 10, Figures 2, 2a 
Elphidotarsius florencae Gidley, 1923, p. 10. 

Type.— V.S.N M. no. 9411, left lower jaw with P4-M3. Collected 
by Dr. J. W. Gidley. 

Horizon and locality. — Gidley Quarry, Fort Union, Middle Paleocene 
horizon, Crazy Mountain Field, Mont. 

Diagnosis. — Sole known species of genus as diagnosed above. See 
also description and measurements below\ 

Discussion. — •P4 is a very peculiar tooth, longer, wider, and liigher 
than Ml although not greatly exceeding the latter in any dimension. 
Both sides are almost smoothly convex, but the apex is formed by 
four cuspules, or serrations, of which th6 second is highest although 
the third is slightly larger. The first three are in a straight anteropos- 
terior line, the fourth slightly more internal. The very short heel has 
one cusp, from which a small sharp crest descends vertically along the 
posteroexternal edge of the tooth and turns into the external cingulum. 

On Ml the distinct but small paraconid and the larger metaconid 
are widely separated and there is no trigonid basin. The metaconid 
is posterointernal to the protoconid. In the talonid the hypoconulid 
cannot be distinguished and the basin is not completely closed, as 
there is a deep narrow notch between the entoconid and the trigonid. 
On M2 the trigonid is much shorter and wider, the metaconid less 
posterior, the paraconid close to the metaconid although still distinct, 
a small trigonid basin present. The talonid is like that of M 1 but larger. 
The trigonid of M3 is like that of M2. The heel is modified by the 
addition of a well-differentiated third lobe, the elevated posterior and 
posterointernal rim of which shows some tendency to split into two 
cusps, although these are not distinctly developed. On Mi the proto- 
conid and metaconid are of nearly equal height. On M2 the protoconid 
is slightly and on M3 decidedly lower than the metaconid 

To an even greater degree than is common in primitive mammals the 
alveolar border slopes outward, so that the external faces of all the 
cheek teeth are much higher than the internal. 

Presumably an enlarged incisor was present, but its root did not 
extend under P4, and the jaw is broken oft" at this point. 



164 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

Measurements of the only known specimen are as follows: Length P4, 
1.5; width P4, 1.2; length Mi, 1.2; width Mj, 1.2; length Mo, 1.2; 
width M2, 1.3; length M3, 1.7; width M3, 1.0; Mi_3, 4.4; ratio length 
P4 : length Mi, 1.25; ratio length Mg : width M2, 0.95; ratio length 
M3 : length M2, 1.42. 

Family PLESIADAPIDAE Trouessart, 1897 

Although quite distinctive and manifestly in the plesiadapid line, 
Pronothodectes shows a definite resemblance to the other primate 
genera in this fauna. Elphidotarsius represents the beginning of a 
divergent line, especially in the first stages of specialization of P4, but 
there is a remarkably detailed resemblance in the molar structure. 
The paraconids are more distinct in Elphidotarsius and the trigonid of 
Ml more expanded anteroposteriorly. The talonid cusps of Mi_2 are 
less distinct. Except for the here very slight difference in the para- 
conid, the higlily characteristic M3 is almost identical in the two gen- 
era. The resemblance to Paromomys, especially P. depressidens, in 
the lower teeth is also very marked, the noteworthy differences aside 
from the divergent emphasis in the anterior teeth being in the some- 
what more progressive, or slightly different, specialization of the molar 
trigonids and the aberrant heel structure of M3 of P. depressidens. 
The trigonid structure, but not that of the heel of M3 is somewhat 
more closely approached in Palaechthon. 

The very incomplete knowledge of Pronothodectes upper teeth sug- 
gests a basic resemblance to those of other genera here described, but 
makes it easier to see a few outstanding differences: the better para- 
cone-metacone separation and strong conule of P* and the less- 
marked posterointernal molar expansion in Pronothodectes, all of which 
are resemblances to Plesiadapis. 

There can be no question that Gidley was right in considering Prono- 
thodectes as closely related to Plesiadapis ("Nothodectes"). The prin- 
cipal differences are clear from the description. Pronothodectes has 
the enlarged incisor less procumbent, tooth reduction considerably 
less advanced and diastema not developed, cheek teeth less depressed 
and of somewhat simpler detail. In all these respects and also in the 
smaller size of its species, Pronothodectes is more primitive than Plesia- 
dapis, to which it seems surely to be ancestral in a structural, and 
perhaps also in a literal sense. 

Pronothodectes represents the earliest known member of a primate 
phylum analogous to the Elphidotarsius-Carpodaptes-Carpolestes 
phylum but with a greater known range in space and time. Its 
principal terms are Pronothodectes, middle Paleocene of North America, 
Plesiadapis, upper Paleocene of North America and Europe and, prob- 
ably, lower Eocene of North America, and Platychoerops, lower Eocene 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 165 

of Europe. The European Cheiromyoides Stehlin is a contemporary 
and close relative of Plesiadapis. 

Nothodedes Matthew is clearly a synonym of Plesiadapis, as pointed 
out by Teilhard and accepted by all subsequent students." Jepsen 
(1930 and 1934) tentatively placed Plesiolestes in this group, but the 
belief that it does not belong here has already been expressed above. 
He also (1934, p. 290) rejects my redefinition (Simpson, 1929c) of 
Plaiychoerops and its separation from Plesiadapis, but I have already 
defended this at some length (1935c). 

Cheiromyoides Stehlin, accepted as valid by Abel, Jepsen, and 
others but rejected as a synonym of Plesiadapis by Teilhard, differs 
less from typical Plesiadapis than does typical Plaiychoerops . It evi- 
dently represents an only slightly divergent and, as far as known, 
sterile side branch of the phylum. 

Genus PRONOTHODECTES Gidley 

Pronothodectes Gidley, 1923, p. 12. 

Type. — P. matthewi Gidley. 

Distribution. — Middle Paleocene, Fort Union, Montana. 

Diagnosis.— Denta] formula 2ori.L3.3" Lower incisor much en- 
larged, semiprocumbent, root laterally compressed. Canine (or 
possibly Pi) small, slightly procumbent. P2 1-rooted. P4 with 
quadrate base, short, high trigonid portion, no paraconid or meta- 
conid. Talonid large with a single cuspule. Paraconid distinct on 
all molars, anteroexternal to the metaconid and progressively nearer 
the latter from Mi to M3. No metast5did, but a vague cusp on the 
hypoconid-trigonid crest. M3 with third lobe and elevated postero- 
internal rim with two or more pooz'ly differentiated apices. P* with 
separate subequal paracone and metacone apices, their bases con- 
fluent, large conule mass, and strong protocone, which is, however, 
less expanded than in Plesiadapis. Upper molars Plesiadapis-\ike 
but simple, without major cremdations or secondary cuspules, and 
probably lacking the mesostyle (although this may be removed by 
wear in the known material). 

PRONOTHODECTES MATTHEWI Gidley 

Plate 8, Figure 1; Plate 9, Figures 2, 11, 12; Plate 10, Figures 3, 3a 

Pronothodectes matthewi Gidley, 1923, p. 12. 

Type.— U.S.N.M. no. 9547, part of right maxilla wdth P^-M^. 
Collected by A. C. Silberling. 

Parafypes.- — U.S.N.M. no. 9332, left lower jaw with incisor root 
and crown of ?C, P2, P4, and M1-3. Collected by Dr. J. W. Gidley. 

8' It is, however, certain that Nothodectes gidleyi Matthew is specifically distinct from the European 
Plesiadapis triscuspidens Gervais. 



166 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

U.S.N.M. nos. 10005 and 10044, isolated upper incisors (pertinence 
dubious). Collected by A. C. Silberling. 

Horizon and locality. — All known specimens from Gidley Quarry, 
Fort Union, Middle Paleocene horizon, Crazy Mountain Field, Mont. 

Diagnosis: — Sole known species of genus. See also description 
below. 

Discussion. — The lower dentition is crowded, with no diastema. 
Ii is a very large, laterally compressed, nearly procumbent tooth. 
Its crown is not known. Immediately above and behind the root of 
Ii is a shallow, very small, and somewhat doubtful alveolus, probably 
for a vestigial I2. The following tooth, probably a reduced canine, 
is also small and 1-rooted. The root is slightly procumbent, the 
rather formless crown more so, as it projects obliquely upward and 
forward from the root. 

While Dr. Gidley did not discuss these anterior teeth, he gave the 
dental formula as 1.1 or 0.4.3. from which he evidently considered the 
first alveolus as doubtful and the tooth just mentioned as a first pre- 
molar. While the question cannot be answered definitely, the formula 
2 or 1.1.3.3 seems to me much more probable. The morphology is 
indecisive, but in later plesiadepids PS are always lacking and in 
probably related groups (especially the tarsioids) are apparently 
among the first teeth to be lost, while the canine is more tenacious, 
being still present in the upper, although not in the lower, jaw of the 
much more advanced genus Plesiadapis and seldom or never absent in 
the tarsioids even though it may be reduced.^* 

P2 is a simple tooth with one vertical root and a slightly procumbent 
crown excavated on the inner side and with a small 1-cusped heel. 
P3 has two roots and is not reduced relative to P4. Its crown is not 
known. P4 is similar to that of Plesiadapis, but its base is more 
quadrate, the trigonid portion is relatively shorter and higher, the 
heel is at least as large, relatively, or a little larger, but its transverse 
posterior crest rises to one apex, rather than two as usual in Plesiadapis. 

The paraconid is distinct on all the molars and is anteroexternal to 
the metaconid. From Mi to M3 it is progressively closer to the meta- 
conid and relatively smaller. The protoconid is about as high as the 
metaconid on Mj, and on M2 is somewhat and on M3 much lower than 
the metaconid. The talonids of Mi -2, which are considerably wider 
than their trigonids, are simple and basined. A hypoconulid can be 
distinguished but is poorly differentiated. There is also a poorly 
developed cusp on the crest from the hypoconid to the posterior base 
of the trigonid. The entoconid-metaconid crest is notched. There 
is no metastylid. M3 is distinguished by the expansion of the posterior 
end and the development of an elevated posterointernal rim, into 

6' Gidley gives the formula ?2.?i or o.?4.3 for the upper dentition, but this- is presumably an inference 
as no specimens show anything more than that there were three upper molars and at least one premolar. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



167 



which enter entoconid and h3^poconulid and on which other, variable 
cuspules are probably developed, although obscured by wear on the 
known specimens. 

The horizontal ramus of the mandible resembles that of Plesiadapis, 
but the symphysis (and incisor) are less inclined, and the constriction 
at the diastema of Plesiadapis is absent, as is the diastema. The 
larger anterior mental foramen is beneath P2 and the smaller posterior 
foramen beneath P4. 

The single upper jaw fragment referable to this species has only 
P*-M", and these are much worn and somewhat corroded. P* has 
the paracone and metacone as well separated as in Plesiadapis, a large 
conule mass usually considered a protoconule in this group, but from 
its central position it could be either this or a metaconule, and a dis- 
tinct protocone apparently higher but less expanded than in Plesia- 
dapis. The molars seem to resemble those of Plesiadapis closely but 
to be somewhat simpler, with few or no secondary cuspules and crenu- 
lations. The anterointernal corner is more evenly rounded, not 
emarginate. No mesostyle can be seen. It may have been removed 
by wear, but probably was absent. 

Table 36. — Individual measurements of Pronothodectes matthewi 
Lower Jaws (all known) 





P4 


M, 


M2 


Ms 


M,-3 


LP4 

LMi 


LMj 
WM2 


LM3 


U.S.N.M. no. 


L 


W 


L 


W 


L 


W 


L 


W 


LM2 


9332 


Mm 
1.8 

1.8 


Mm 
1.6 
1.6 


Mm 
2.0 
1.9 
2.1 
2.1 


Mm 
2.0 
1.9 
2.0 
2.0 


Mm 
2.0 
2.0 
2.1 


Mm 
2.1 
2.1 
2.3 


Mm 
3.1 
3.2 
3.1 


Mm 
1.8 
2.1 
2.1 


7.3 
7.3 
7.4 


0.90 
0.95 

0.81 


0.95 
0.95 
0.91 


1.55 


9531 

9443— 


1.60 
1.48 


9847 


1.7 


1.9 



















Upper Jaw (unique specimen) 



U.S.N.M. no. 


P< 


Ml 


M2 


LP* 
LM' 


WM3 




L 


W 


L 


w 


L 


W 


LM2 


9547 


Mm 
1.9 


Mm 
2.7 


Mm 
2.0 


Mm 
3.2 


Mm 
2.1 


Mm 
3.5 


0.95 


1.67 







Genus PLESIADAPIS Gervais, 1877 

PLESIADAPIS REX (Gidley) 

Plate 9, Figures 4, 13 

Tetonius rex Gidley, 1923, p. 11. 

Type.—U.^.^M. no. 9828, isolated M2. Collected by A. C. 
Silberling. 

119212—37 12 



168 BULLETIiSr 16 9, UNITED STATES NATIONAL MUSEUM 

Horizon and locality. — Loc. 13,^^ Fort Union, Upper Paleocene 
horizon, Crazy Mountain Field, Mont. 

Diagnosis. — A poorly characterized species with M2 very low and 
broad. Dimensions of type Ms, 3.7 by 3.6 mm.^" 

Discussion. — Gidley compared this isolated tooth in a broad way 
to Absarokius and Tetonius, but his reference to Tetonius was clearly 
Intended to be merely provisional. The resemblance exists, of course, 
but is not exact, and the tooth more nearly resembles M2 of Plesiadapis, 
which was poorly laiown to Gidley when he was working on these 
primates. This is a more probable reference, although it cannot be 
definitive on the basis of one tooth. The size is slightly, but signifi- 
cantly, larger than for M2 of P. gidleyi, and the crown is slightly lower. 
There is a closer resemblance to P. anceps of the Scarritt Quarry, but 
the crown has a broader, blunter aspect. 

A lower incisor figured by Gidley (1923, pi. 3, fig. 13)''^ probably 
belongs to this species. It very closely resembles the corresponding 
tooth of P. gidleyi. 

Among the specimens found by Silberling and me at Loc. 13 in 1932 
a,re two probably referable to this species. One is a right Mi, like 
that of P. anceps except for its wider lower aspect and stronger external 
cingulum. It measures 3.3 by 3.1 mm. The other is an upper incisor 
also resembling that of P. anceps but consideral^ly heavier and wider 
relative to its labiolingual diameter, the lateral apical cusp large and 
directed more laterally, and with marked rugosities and small sec- 
ondary cuspules on its lingual face. There is also a slightly smaller 
but otherwise almost identical tooth from this locality in the Princeton 
collection. 

When I described Plesiadapis anceps, from a lower level near Loc. 
13, I was not aware that Tetonius rex Gidley belonged (in all prob- 
ability) to Plesiadapis. The species may be synonymous, in which 

6' This was published as from Loc. 12 and bears that datum on the label, but it seems certain that this 
is not the locality in sec. 30, T. 6 N., R. 15 E., which we relocated in 1932 and which Mr. Silberling then 
noted as Loc. 12. Id the first place, he records only invertebrates, no mammals, from that locality. In 
the second place, it is low in the Fort Union No. 3, and less than 550 feet above the Gidley Quarry, strati- 
graphically, whereas Gidley's published and manuscript data say "nearly 4,000 feet higher in the beds than 
in the 'Gidley Quarry' and 'Silberling Quarry' levels", which is approximately true of Locs. 11 and 13. In 
the third place, Gidley's data give locality "No. 12" in sec. 22, T. 5 N., R. 14 E., and Loc. 13, but not 
Silberling's Loc. 12, is in that section. Loc. 11 was formerly thought also to be in that section, but in 1932 
it was relocated as across the line in section 23. In the fourth place, we found other material apparently 
of the same species at Loc. 13, and at no other horizon or locality. And finally. Dr. Gidley himself seems 
to have been in some doubt about this locality, for on a label of some other material he has noted "No. 12 
(?13)", whereas there could hardly be any question about the distinction between the localities now recog- 
nized as 12 and 13, since they are at widely different horizons and far from each other in the field. It seems 
certain that the true type locality of this species is either Loc. 13 or Loc. 11 and highly probable that ic is 
13, although this point does not matter as 11 and 13 are near each other and at the same level. 

"» Gidley gives 3.8 by 3.S mm, which is as close an agreement as is probable in measurements by different 
workers. I have thought best in all cases to give my independent measurements, so that they are more 
likely to be comparable throughout this paper. 

"' The figure is of the outer side of the tooth, peculiarly oriented, and is not very characteristic. The 
legend gives 12 as its locality, but the label says "12 {?13)", and for the reasons already given I am confi- 
dent that it is really from Loc. 13, at least as they are now numbered. 



FORT UXIOX OF CRAZY MOUXTAUST FIELD, MONT. 



169 



case P. rex (Gidley) has long priority. If, however, all the material 
described above belongs to P. rex, it is almost surely distinct from 
P. anceps, and even if this is not the case it is not certain from the 
types that they are the same. In any event it is preferable to retain 
the name P. anceps for the present, as it is a well-lmown and well- 
characterized species, whereas P. rex is as yet very poorly known and 
its specific characters are not really established. The difference in 
stratigraphic level between the horizons of the two types is nearly a 
thousand feet. 



Order TAENIODONTA Cope, 1876 

Family STYLINODONTIDAE Marsh, 1875 

Matthew (Pale. Mem.) is followed in referring all 
taeniodonts to a single family (with four subfamilies). 
This is an extremely rare group in this fauna, with only 
four specimens in the National Museum collection. 

Subfamily Conoryctinae Matthew, 1937 
(Conoryctidae Wortman, 1896) 

Genus CONORYCTES Cope, 1881 

CONORYCTES COMMA Cope, 1881 

Figure 34 




Figure ^i.— Conoryctes 
comma Cope, U.S.N.M. 
no. 9597, upper molar: a, 
External view; b, crown 
view. Natural size. 



Wortmann and Matthew recognized only one species of Conoryctes 
in the Torrejon, and as far as I know none has ever been described from 
any other formation. U.S.N.M. no. 9597, an isolated upper molar 
from the Gidley Quarry; no. 9678, isolated P^ from the Silberhng 
Quarry; and no. 9816, two upper molars from Loc. 6, seem to be in- 
distinguishable from Torrejon specimens. No. 9826, from Loc. 28, a 
higher level, may belong to Conoryctes but is not determinable. 

Subfamily Psittacotheriinae Matthew, 1937" 

Genus PSITTACOTHERIUM Cope, 1882 

PSITTACOTHERIUM MULTIFRAGUM Cope, 1S82 

Douglass (1908, p. 22) recorded a Calamodon in the Fort Union, 
querying the generic reference. Matthew (1914, p. 390) commented 
on Douglass' pubUshed data that this material "agrees better with 
Psittacotherium." In the National Museum collection there is a speci- 
men, no. 6162, from the level of and near the Silberling Quarry, which 
includes parts of two canines, two complete cheek teeth, and other 

'" Matthew (Pale. Mem.) places the calamodonts and stylinodonts in the Stylinodontlnae and separates 
the psittacotheres as a distinct subfamily. 



170 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

fragments. This agrees very closely with Torrejon specimens referred 
to Psittacotherium multi/ragum, and judged from his figures and 
descriptions the same is true of Douglass' single tooth. The generic 
reference is beyond doubt, and the specific reference highly probable." 
The species is surely and the genus probably different from IPsitta- 
cotherium lohdelli Simpson, 1929, from Bear Creek, which is definitely 
more advanced. 

Order CARNIVORA Vicq d'Azyr, 1792 
Suborder Creodonta Cope, 1875 

Matthew has repeatedly discussed and carefully defined this primi- 
tive carnivore suborder, which includes all known Paleocene carni- 
vores. The only serious criticism that has been made of liis general 
arrangement (for instance by Wortman or Osborn) is that the Mia- 
cidae, being structurally ancestral to the Fissipedia, shoidd be placed 
in the latter group. This would be in accord with phylogenetic classi- 
fication, but as Matthew protested and as most students must agree, a 
completely phylogenetic classification is a practical impossibility. 
Tliis case is one in which departure from it seems desirable and 
necessary. The Miacidae have many characters allying them with 
creodonts and cutting them off from their descendants the fissipedes 
and furthermore if they are removed from the Creodonta that group 
ceases to exist not only as Cope defined and conceived of it but also as 
a natural and practical group. Alatthew's retention of the "hori- 
zontal" unit Creodonta, including the Miacidae, seems sound and is 
adopted here. 

In the Paleocene there are five typical groups of creodonts: Oxy- 
claeninae, Arctocyoninae, and Triisodontinae (these three subfamihes 
forming the Arctocyonidae), Mesonychidae, and Miacidae (Viverra- 
vinae only in the Paleocene).''* Of these the Oxyclaeninae are far the 
most primitive, without carnassial teeth and with decidedly generalized 
dentition and skeleton. The Arctocyoninae are also primitive and 
indeed intergrade with the Oxyclaeninae but are generally larger forms 
with flat, broad, bearlike teeth. The Triisodontinae are without 
shearing teeth but with pecuHar blunt, heavy, and extremely simple 
teeth (probably secondarily in part). The Mesonychidae, so aberrant 
that they have been excluded from the Carnivora (Gregory) although 
probably belonging there (Matthew), developed a pseudotriconodont 
and semihomodont lower dentition and are still more strildngly 

'3 The Torrejon specimens show great variation, and Cope named three species, which were, however, 
considered synonyms by Wortman. Matthew (Pale. Mem.) believed it possible that more than one species 
occurs there but did not redefine them separately. 

'< Other groups begin to appear before the nominal end of the Paleocene, but they seem to be Eocene fore- 
runners, not typically Paleocene mamm als. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 171 

characterized by some strangely ungulatelike limb characters. The 
Miacidae had typical carnassials as in fissipedes and were generally 
progressive and adaptive. 

All five groups are rather abundantly represented in the Torrejon 
in individuals, although only the Oxyclaeninae there show much 
variety in genera and species. In the present fauna the Oxyclaeninae 
are also abundant and varied, relatively about as in the Torrejon, 
although all the species and most of or all the genera are here different. 
The Arctocyoninae are not abundant but are apparently more varied 
than in the Torrejon. Triisodonts, common Torrejon fossils, are 
absent in this fauna as now known, and the mesonychids are repre- 
sented only by extremely rare fragments. Miacids, on the other hand, 
are present and are more varied than in the Torrejon. 

Family ARCTOCYONIDAE Murray, 1866 '' 

This is one of the groups so largely and adequately defined and dis- 
cussed in Matthew's memoir that redefinition here is quite unneces- 
sary. The genera placed in the Arctocyonidae have commonly been 
distributed in the Oxyclaenidae, Triisodontidae, and Arctocyonidae 
since Scott (1892) defined the first two families. 

Osborn and Earle (1895) also proposed a family Chriacidae, but this 
was rather a substitution for Oxyclaenidae (because they considered 
Oxyclaenus, proper, as incertae sedis) than a separation from it. 
Matthew (1897) provisionally proposed the use of Chriacidae for 
Chriacus, "Protochriacus" {Loxolophus) , and Tricentes if, as he then 
suspected, Oxyclaenus were referable to the Triisodontidae. The 
latter step was not taken. Oxyclaenus and Triisodon were eventually 
placed by Matthew in the same family, Arctocyonidae, but Chriacus 
was also placed there. The earlier work adumbrated a fourfold 
division, with groups typified by Oxyclaenus, Chriacus, Arctocyon, and 
Triisodon. Various of these were at times separated mdely, but the 
way in which some genera were shifted from one to another and all 
sorts of combinations made shows how hard it really is to tell these 
groups, or supposed groups, apart. 

In his latest work, Matthew (Pale. Mem.) took the logical step of 
reuniting all these genera under the oldest family name, Arctocyonidae. 
It seems to be demonstrated that all are rather closely related and 

» I would prefer to give, and in some earlier publications have given, as author of a family the first writer 
who recognized the group and gave it a name based on a valid genus, even if he did not follow the family 
form now maintained. This would make Giebel, who named the Arctocyoninae in 1855, author of the 
Arctocyonidae. In fact he was, aside from quibbling, for his group Arctocyoninae was distinguished from 
nonarctocyonids, not from other arctocyonids (none of which were then known) and was, as far as then possible, 
the group we now call Arctocyonidae. In reality, then, Giebel is the author of this family, but the bibliog- 
raphers will not have it so and, of course, they are correct in the letter of the law, if not in a spirit of justice. 
On the grounds of literal correctness and largely of feeling that the purpose of quoting authority is not to 
honor but only to define, I have abandoned my former practice. This statement applies to a number of 
other groups as well as to this. 



172 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

even if the supposed groups are separable, they do not all together 
exceed the usual limits of a single family of carnivores. 

Matthew subdivides the family into Oxyclaeninae, Chriacinae, 
Arctocyoninae, and Triisodontinae. These are essentially the old 
families, except that the Chriacidae of Osborn and Earle and (tenta- 
tively suggested, not adopted) of Matthew was merely the Oxyclaeni- 
dae with Oxyclaenus excluded, while the Chriacinae of Matthew's 
last work is based on quite a different concept and includes only 
Chriacus and Deltatherium. 

Despite the name of the family, its central, most varied, and most 
typical group is that of the Oxyclaeninae. Separation of the Trii- 
sodontinae seems justified, since these animals (not yet identified in 
the present fauna) are of a peculiar adaptive type only the earliest 
examples of which show close approach to oxyclaenines. The Arcto- 
cyoninae form a clear-cut group if contrasted with such types as 
Oxyclaenus or Chriacus, but such genera as Protogonodon, Tricenies, 
Arctocyonides, or Thryptacodon, each in a different way, tend to 
bridge the morphological gap and to make clear differentiation difficult 
or impossible. Perhaps in the fanlike radiation of this potent and 
extremely varied family several lines approached a beariike, omniv- 
orous adaptive type and the Arctocyoninae may be a partly artificial 
concept uniting several of the more extreme adaptive types inde- 
pendently trending in tliis direction. Despite this possibility, the 
concept is a practical one and may well be adopted pending a better 
understanding of the actual phylogeny. 

The idea of separating Chriacus from the Oxyclaeninae seems less 
fortunate, and it is probably impractical at present. The Arcto- 
cyonidae -wdth the Triisodontinae and Arctocyoninae removed are 
a hodgepodge including many different lines each potentially or 
actually as distinct as that suggested by Chriacus. These numerous 
minor phjda are so intricately interrelated and most of them are so 
poorly known that a good subfamily or supergeneric arrangement is 
not now attainable. It does not seem helpful to separate one genus, 
Chriacus, which is probably no more distinctive than each of a dozen 
others. From another viewpoint the inadequacy of such an arrange- 
ment is also shown by the discovery of such a type as Metachriacus , 
which might roughly be characterized as "chriacine" in premolars 
and "oxyclaenine" in molars. With the greatest respect for Mat- 
thew's incomparable knowledge of these faunas and clearness of 
judgment it further seems to me that his collocation of Deltatherium 
is based on superficial characters and that this genus differs more from 
Chriacus than does any of several genera not placed in the Chriacinae. 

The present fauna contains certainly six and possibly seven genera 
of Arctocyonidae. Five of these were defined from this fauna and 
have not definitely been recognized elsewhere. Of the Crazy Moun- 



FOKT UNION OF CRAZY MOUNTAIN FIELD, MONT. 173 

tain arctocyonids, Claenodon belongs in the Arctocyoninae. Deutero- 
gonodon might be placed there or in the Oxyclaeninae, or even in the 
Condylarthra. In default of better evidence and for ease of subfamily 
recognition it is placed in the Arctocyoninae, which it most resembles 
in adaptive characters although perhaps not phyletically close to 
other members of that group. 

Alimotricentes is a typical but well-differentiated oxyclaenine. 
Prothryptacodon seems surely to be in the lineage of Thryptacodon, 
with which it forms a rather distinctive phylum retained in the 
Oxyclaeninae, where Thryptacodon has generally been placed. Meta- 
chriacus is an oxyclaenine in the broad sense. If Oxyclaeninae and 
Chriacinae were separated, this genus would be incertae sedis, for it 
resembles both groups. Spanoxyodon is also clearly oxyclaenine, 
sensu lato, and might doubtfully be an aberrant chriacine if that 
group were retained. The occurrence of Chriacus in the fauna is 
possible, but not proved, and no additional evidence on the affinities 
of that genus is here adduced. Coriphagus, with which the Torrejon 
Mixoclaenus is synonymous, was classified by Matthew in the Oxy- 
claeninae, but I believe it to be an anisonchine, as set forth in dealing 
with that group. 

The members of this family are the most primitive of known carni- 
vores, and, as might be expected, they are abundant in all Lower and 
Middle Paleocene faunas. In the Upper Paleocene they are less 
varied and comm.on, and as far as known they died out by the end of 
lower Eocene time. The Middle Paleocene forms are prototypal in 
a general, structural sense, but are already too late to be ancestral 
to other groups. Matthew (Pale. Mem.) has pointed out the great 
interest of the family as probably including in its Lower Paleocene or, 
especially (unknown), pre-Paleocene members the probable ancestry 
not only of all carnivores but also of other orders, including most or 
all ungulates and some others. Despite the numerous minor struc- 
tural modifications, most members of the family have almost diagram- 
matic tuberculo-sectorial teeth such as are believed to be primitive 
for all marsupial and placental mammals. The osteological characters 
of the group as a whole are also primitive for the great majority of 
placental mammals, many of them for all these, but on these characters 
the present materials have practically nothing to add to what is known 
from the Puerco and Torrejon mammals. 

Subfamily Arctocyoninae Giebel, 1855 

Claenodon and Deuterogonodon represent this subfamily in the 
present fauna. The status of a supposed third genus, Neoclaenodon, is 
discussed below. Deuterogonodon might be considered an oxyclaenine, 
in view of its resemblance to Protogonodon, which Matthew so classi- 



174 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

fies, but its adaptive characters, at least, are more arctocyonine and 

the groups are more easily defined if it is placed here. It may not 

really be a creodont. 

Genus CLAENODON Scott 

Claenodon Scott, 1892, p. 298. 
Synonym: Neoclaenodon Gidley, 1919. 

This group was studied by Dr. Gidley and the results published 
(1919), his manuscript notes including no further observations. One 
specimen, of considerable interest, has since been added to the Na- 
tional Museum collection (by Silberling and me in 1932), and there are 
several specimens in the Princeton collection that were not included 
by Gidley in his publication. Dr. Gidley also studied Cope's types 
and at least two later American Museum Torrejon specimens (A. M. 
nos. 16543 and 16545), but he apparently did not examine the whole 
American Museum series, wliich includes about 50 specimens. On 
this basis I am forced to adopt a broader view of the variability of 
the group and to modify the generic and specific criteria used, thus 
arriving at a modified systematic arrangement, which also differs from 
the final conclusions of Dr. Matthew (Pale. Mem.), based on American 
Museum material only. 

With one exception, the Fort Union specimens were all referred by 
Gidley to a new genus, Neoclaenodon. The supposed generic char- 
acters as given by Gidley (1919, p. 547) may be listed and commented 
on as follows: 

1. "Cranial portion of skull relatively long and deep; interorbital 
space apparently much narrower, and postorbital constriction longer 
and more slender than in Claenodon." This is based on a comparison 
of two specimens, one of Claenodon "corrugatus" and one of "Neo- 
claenodon" montanensis, as no others yet discovered show these 
features. They are crushed in opposite ways, which accounts for 
part of the difference in aspect. Tliis individual of "N." montanensis, 
however, probably does have a slenderer and longer midcranial region, 
but this is a character so variable with age, so likely to be of merely 
specific value at best, and so impossible to use on a practical basis 
for the separation of the fossil species that, in itself, it does not carry 
generic weight. 

2. "Anterior premolars, upper and lower, much reduced; in upper 
jaw distinct diastemae behind P', and between P^ and P^; the first 
premolar, above and below, lies closely appressed to the canine." 
This is in part distinctive from some specimens of C. Jerox, and not 
from others. The influence of selecting particular specimens for 
comparison is seen in the fact that Matthew (Pale. Mem.) proposed 
to redefine Neoclaenodon as having the premolars unreduced [relative 
to Claenodon]. In fact the whole series with its various species is 
variable in these characters and varies, as far as apparent, about a 



FOKT UNIOX OF CRAZY MOUNTAIN FIELD, MONT. 175 

single mode. These premolar characters are certainly not generic 
and probably not good specific characters. 

3. "Hypocone in M^ and M^ rudimentary." This is a fairly clear 
distinction from any Torrejon specimen known to me. The species 
montanensis may be distinguished by having the hypocones of M^~^ 
slightly smaller than the smaller variants of other known species. 
If tliis be made a generic character, however, it would be almost the 
sole character defining the genus and the genus would be monotypic^ 
as even Gidley's "Neoclaenodon" silherlingi probably had hypocones 
proportionately as in the larger species. 

4. "Hypocone . . . wanting in M^; M^ much reduced, suboval in 
outline with relatively small metacone." Tliis again applies only to 
a very limited extent to 'W." silherlingi. Furthermore, in the 
Torrejon species usually (but incorrectly) called C. protogonioides 
some specimens have corrugatus-like M^ and others that are, never- 
theless, surely conspecific have M^ almost as in "N." montanensis. 
C. jerox has relatively larger M^, but the hypocone is often lacking. 
The character is obviously somewhat variable and when well marked 
of specific, not generic, character. 

5. Various skeletal characters (all repeated in the extended descrip- 
tion quoted below) are also given. Here it need only be said that, 
as Gidley points out, the basic structure is quite as in Claenodon. 
Some characters, as the fusion of scaphoid and centrale (not, however, 
considered diagnostic by Gidley) or the broad astragalus (which was 
considered diagnostic), although apparently fundamental, are indi- 
vidually variable in C. Jerox. None is more important than the 
slight structural modification to be expected in smaller and larger 
species of one genus. 

Matthew (Pale. Mem.) accepts Neoclaenodon as probably valid 
but rejects all Gidley's characters as not being diagnostic of the 
genus. He does not clearly redefine it but mentions its smaller 
size, unreduced premolars, and lack of heavily rugose enamel. The 
smaller size (about 25 percent) is surely not a generic character. 
The supposed difference in premolar reduction is probablj^ subjective, 
as already suggested: Matthew says the premolars are less reduced 
than in Claenodon, and Gidley says they are more reduced. They 
seem to me to be about the same, taking each supposed group as a 
whole. The rugosity of the enamel is about the same proportionately 
in "A^." montanensis as in C. jerox but is probably less in C. ''pro- 
togonioides.'' 

Matthew's acceptance of Neoclaenodon is based on the Torrejon 
species that has generally been called Claenodon protogonioides. 
This name is not applicable in tliis way, as it belongs to a Puerco 
species (probably of the genus Protogonodon) , and Matthew proposes 
a new name (Pale. Mem., unpublished at the time this was writ- 



176 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

ten). He places the species in Neoclaenodon and bases his ideas of 
Neoclaenodon on it, apparently overlooking the fact that this would 
exclude its own genotype from this genus. Indeed "N." montanensis 
resembles Claenodon ferox in several points, which are differences 
from the Torre j on species liitherto confused with protogonioides, 
such as the more rugose enamel, the stronger and crenulated cingula, 
and the shelf-like, rather than conical, protocone on P"'. On this 
basis the small Torrejon species might (but in my opinion should not) 
be placed in a new genus, but the genus would not be Neoclaenodon. 

Thus, while there are single characters on which genera might be 
founded, none of these seems either well marked or higlily significant, 
nor are they combined in such a way as to support the separation ot 
Claenodon and Neoclaenodon as proposed either by Gidley or by 
Matthew. The upshot of using such characters would be to force 
the erection of a genus for each well-defined species, a procedure not 
useful and concordant with the really close resemblance of all members 
of this group. 

The species previously recognized or proposed are as follovv^s: 

Claenodon ferox (Cope, 1883). Genotype. 

C. corrugatus (Cope, 1883). 

C. sp. innom. (Matthew, Pale. Mein.)i="C. protogonioides", pars, of authors 
(in error). [C. procyonoides (Matthew, 1937) ; published too late to insert through- 
out the present bulletin.] 

C. montanensis (Gidley, 1919). Genotype of Neoclaenodon. 

C. silberlingi (Gidley, 1919). 

C. latidens (Gidley, 1919). 

Of these, I consider C. corrugatus as a synonym of C. Jerox, and 
C. silberlingi and C. latidens as of doubtful validity, one or both pos- 
sibly being synonymous with C. montanensis. Another species, C. 
vecordensis has been described from the present fauna. 

In comparing some of the Fort Union specunens with the Torrejon 
material and in considering the general nature and limits of variation 
and the validity of specific distinctions in this group, it has been 
necessary to restudy the Torrejon specimens. These have in the 
past been referred to tlu-ee species, following Cope, C. jerox, C. cor- 
rugatus, and C. protogonioides. The type of C. protogonioides is from 
the Puerco, and Matthew (Pale. Mem.) has shown that it belongs in 
Protogonodon and that the Torrejon specimens hitherto placed there 
do not belong to it but to an unnamed species (named in Pale. Mem.), 
surely distinct from C. Jerox or C. corrugatus. 

C. corrugatus was distinguished from C. ferox by Cope as being 
smaller and with the hypocone somewhat better developed. The 
latter character is variable and, in the extremely slight degree in- 
dicated by the types, seems to be individual. Matthew (Pale. Mem.) 
considers C. corrugatus as of doubtful status but redefines it as smaller, 
with less robust premolars, inner cusps less developed on P^~*, de- 



FORT UXIOX OF CRAZY MOUXTAIX FIELD, MOXT. 



177 



<;idedly smaller and slenderer canines, limb and foot bones smaller 
and of slenderer proportions throughout. 

I am at a loss to understand the supposed distinction of the inner 
cusps of P^~"* as I find no specimen identified by Matthew as Cjerox 
that has those teeth. The number of specimens in which the canines 
are surely associated with cheek teeth is limited, but the measurements 
and ratios shown in table 37 can be taken from the collection. 



Table 37. — Measurements of canines and molars of species of Claenodon 



A.M.ISr.H. no. and species 



Ml 



Mi 



C 

M> 



Ml 



3268 (type C.ferox) 

2456 (neotype C. conugatus) . 

16545 (ref. C. corrugatus) 

16001 '(ref. C. corrugatus) 

32711 (ref. C.ferox).. 

3266 ' (ref. C. corrugatus) 



Mm 
12.9 
8.3 

11.2 



Mm 
11.1 
10.5 
10.0 



Mm 



Mm 



12.5 



1.16 
0.79 
1.12 



10.0 
10.2 



11.0 
10.6 
11.2 



0.62 

0.91 
0.96 
0.78 



' Not identified by Matthew, Pale. Mem., earlier references. 
» Doubtfully referred by Matthew, Pale. Mem. 

No. 3271, with the smallest cheek teeth, has the largest canine 
among the lower jaws, and no. 2456, with the largest cheek teeth 
among the lower jaws, has the smallest canine. Indeed among the 
lower jaws the relative canine size varies inversely with the cheek- 
tooth size, the exact opposite of the hypothesis on which the species 
are separated. Among the upper jaws the largest cheek teeth are 
associated with the relatively largest canine, medium-sized cheek 
teeth with the relatively smallest canine, and the smallest cheekteeth 
with relatively middle-sized (but in ratio nearer the relatively largest) 
canine. The samples are too small for extended statistical study, 
but it is quite obvious that the smaller individuals are not charac- 
terized by relatively small canines, and hence that the supposed 
specific distinction in this character is invalid. Beyond that no 
regular correlation of gross size, or cheek-tooth size, with relative 
canine size is suggested or possible on these data. It is suggested 
that canine size is extremely variable and that both large and small 
cheek teeth may be associated with both relatively large and small 
canines. There is perhaps a sexual distinction in relative canine size 
in addition to or instead of in absolute cheek-tooth size, but this is a 
hypothesis that the data are inadequate to test. 

The smaller premolars and slenderer skeleton supposedly distinctive 
of C. corrugatus cannot be more exactly checked, and the results are 
similar: they are smaller, because they belong to smaller individuals, 
but there is no apparent correlation of relatively smaller premolars 
or relatively slenderer limbs wdth the smaller individuals. 



178 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

The distinction thus is reduced to a matter of size. To judge this 
I have taken a single dimension, the length of M2, because it seems to 
be a valid indication of cheek-tooth or gross individual size and can 
be measured in a relatively large number of individuals. Other 
dimensions give similar results and all need not be published here. 
There are in all 24 individuals of the genus Claenodon from the Torre- 
jon in the American Museum collection in which the length of M^ 
can be measured. The small species hitherto confused with C. pro- 
togonioides is obviously distinct, and the following data apply only 
to the C. ferox-corrugatus group. 



4; 5-1 



CoJculatec/ probable ^Nzotypa^C. corrugatus^ 
position of type^'] ( 

Type,C.feroX' 



C. corvugatas. 
f — Type, C. n. sp. Ma tth 



lew. 



£ 



^ 7.8 8.3 8B 9Z 9.8 10.3 10.8 11.3 11.8 12U3 )?.8 13.3 13.8 M.3 

Figure 35.— Histogram of lencth of M2 of Claenodon from the Torrejon of New Mexico in the American 

Museum. 



The statistical data on the length of Mg of the group are as follows: 

Number in sample 18 

Observed range 11. 5 - 13. 9 

Mean 12. 68± 0.25 

Standard deviation 1. 06± 0.18 

Coefficient of variation 8. 3 ± 1.4 

Contrary to some (e.g., Klahn) of the few paleontological workers 
who have used any statistical data but the most elementary, I can- 
not agree that the extent of variation ("Variationsbreite"), in this 
case 2.4 mm (11.5 to 13.9), has any valuable connotation, being so 
dependent on accidents of sampling that the probable error is enormous. 
The same fundamental idea is more correctly conveyed by the stand- 
ard deviation. The above data are calculated from raw measure- 
ments to 0.1 mm, but in the histogram (fig. 35) these are grouped in 
units 0.5 mm wide, because of the small size of the sample and because 
0.1 is certainly too refined a measurement and below the limits of 
mechanical error and errors due to crushing of the specimens, etc. 



FORT UNIOX OF CRAZY MOUNTAIN" FIELD, MONT. 179 

The onl}^ deflection in the frequency curve is in the 12.05-12.55 group, 
and this is not significant. By actual calculation, which need not be 
given here, a deflection at this point would have to be of at least 3 to 
have any probable significance, and tliis deflection is in fact only of 1. 
The mean, the median, and the mode almost exactly coincide. 

The distribution thus indicates a unimodal, unskewed curve, and 
provides no warrant for splitting into two groups, or species, on the 
basis of size (or of this dimension, which is sufficiently closely cor- 
related with size). 

The actual positions of the types are indicated on the histogram. 
The neotype of C. corrugatus, although not elsewhere formally so 
designated, is such essentially as Matthew (Pale. Mem.) largely bases 
his redefinition of the species on it. The type of C. corrugatus has no 
Ma, but it must have measured about 12.0 mm in this dim^ension, calcu- 
lated from the ratios of associated M^ and M2 in surely conspecific 
individuals of about the same size. M2 of the neotype of C. cor- 
rugatus is 12.4 mm in length and of the type of C. ferox 13.4 mm.^* 
The deviations of these three specimens are: C.jerox, type, +0.72; 
C. corrugatus, plesiotype, —0.28; C. corrugatus, type, calculated, 
— 0.68. All these deviations are considerably less than the standard 
deviation. There is no reason or warrant for placing these individuals 
in different species on the basis of size.^^ 

The coefficient of variation, 8.34, is high and indicates a species of 
considerable variability in size, but there are many cases of dimen- 
sions of single species, and even of subspecies or pure races, with 
equally high variabiUty, or higher, and this figure does not in itself 
suggest that two species, inseparable on these data, may be present. 

These data do not prove that two species are not present: Such 
proof of a negative is practically impossible, and the burden of proof 
is always to be considered as rec^uired from the positive side. They 
do show that in this sample it is impossible to distinguish two size 
groups (and hence two species distinguished by size differences), that 
the distribution is not inconsistent in modality, variability, etc., with 
a single species, and adding considerations somewhat beyond purely 
statistical treatment, that if two species were present they would very 
probably not correspond with those now recognized. 

There are no other variates or attributes, so far as I can observe, 
that do permit any differentiation of this group into two or more 
species. The supposed species occur together, at the same horizon 
and localities, and in approximately eciual numbers."^ 

'6 It ii crushed and spread a little, but this can be exactly allowed for. 

" It may also be noted that on the purely hypothetical and extremely improbable supposition that two 
species were present and that their size limit corresponded with the deflection in the frequency curve given, 
the neotype of C. corrugatus would belong with C. ferox and the type of C. corrugatus would be on the bound- 
ary between the two groups. 

" This, of course, depends on individual identifications, but if these were to be based on any rational 
size distinction the grouping would have to be into two approximately equal groups. 



180 



BULLETIX 16 9, UNITED STATES XATIOIv'AL MUSEUM 



In short, C. corrugatus and C. Jerox are not distinguishable on any 
correct factual basis derived from the known specunens, and they 
must be considered synonymous, the name C. jerox being retained for 
the species. The value of the coefficient of variation maj^ be taken 
as indicative of the degree of variability to be expected in the same or 
analogous dimensions in species of this genus. 

The relationships of the genus Claenodon as a whole have been 
widely discussed and are summed up so thoroughly by Matthew 
(Pale. Mem.) that no details need be given here. It is a typical 
arctocyonid, very close to Arctocyon itself, and in its larger species, 
at least, forerunner of the lower Eocene Anacodon, after which the 
line evidently became extinct. Relationship with the bears has often 
been suggested and was favored by Dr. Gidley, but it is almost cer- 
tainly erroneous. There is very little question that bears developed 
from dogs during the Middle or Later Tertiary and that the limited 
convergence to them shown by Claenodon involves habitus characters 
only and denotes a convergence in food and other habits, but not 
any special affinity. 





Figure Z6.— Claenodon feroz (Cope), tentatively referred specimens from the Melville (Fort Union No. 3): 
a, U.S.N.M. no. 61.56, left M2; 6, Princeton Univ. no. 13755, right Mi, probably from Loo. 44; c, same data 
as 6, left Ma-3 and heel of Mi; d, same data as b, right M'-^, M' broken; e, Princeton Univ. no. 13756, left 
M'-', Ml broken, probably from Loc. 49. All natural size. 

CLAENODON FEROX (Cope, 1883) 

Figure 36 

U.S.N.M. no. 6156, a left^^ Mg and some other fragments, from 
well up in Fort Union No. 3, was tentatively referred by Gidley (1919, 
pp. 545-547) to Claenodon Jerox, with the reservation that better 
material might prove that a new species is represented. Gidley noted 
several distinctions from characteristic C. Jerox of the Torrejon but 
suggested that all could be due to individual variation, except, perhaps, 
the fact that in the Montana specimen the talonid is narrower than 
the trigonid. This, however, is also within the range of variation of C. 



" Gidley, 1919, p. 545, says "right", obviously a lapsus calami. 



FORT UXIOX OF CEAZY MOUNTAIN FIELD, MONT. 181 

jerox, and there are Torre] on specimens practically identical vAih. that 
from Montana in size and structure. The specimen probably does 
represent C. Jerox, but the single tooth is inadequate for certain deter- 
mination. The same statement applies to no. 9651, an isolated left P*, 
from Loc. 53. 

There are several Princeton specimens of Claenodon from their 
cluster of localities in Fort Union No. 3 near the center of the field. 
These all appear to represent one species, with considerable variation 
but not beyond that usual for this group. Morphologically they are 
within the limits of the C. jerox group and cannot be separated from 
that species. 

CLAENODON MONTANENSIS (Gidley) 

Figures 37-39 
Neodaenodon monianensts Gidlky, 1919, p. 547. 

TyjM. — U.S.N.M. no. 8362, much of the skull and jaws with most of 
the dentition, parts of fore and hind lunbs, and other fragments. 
Collected by A. C. Silberling. 

Horizon and locality. — Gidley Quarry, Fort Union, Middle Paleo- 
cene horizon, Sweetgrass County, Mont. 

Diagnosis. — Gidlc}^ (1919, p. 550): "About one-fifth smaller than 
Claenodon Jerox and C. corrugatus, slightly larger than C. protogoni- 
oides (Cope); face relatively short, rostrum deep; brain-case very 
small and elongate; postorbital constriction long and slender; posterior 
root of zygoma depressed below the basioccipital plane (probably a 
primitive character and of much more than species significance), 
giving a decidedly arched contour to the main portion of the skull 
viewed from the side; anterior border of orbit directly above anterior 
boundary of m^; infraorbital foramen directly above middle of p^; 
the large, moderately recurved, slightly compressed canines with 
root-portion much swollen and in contour difficultly distinguishable 
from the crown into which it merges without any deviation in outline; 
1st premolar, upper and lower, single-rooted, relatively large (com- 
pared with p-) and closely appressed to the canine; p^ and p* trian- 
gular, three-rooted, p* with incipient protocone; upper m^ ^^ suboval 
in outline, much reduced with low external cusps, the metacone 
relatively small and inwardly placed; pa and p4 with small, narrow, 
single-cusped heels; lower jaw relativel}^ thin and deep with the lower 
border of its anterior half but slightly curved. 

"Measurements 

Length of uppei* dental series, C to M^ (estimated) 63.1 mm. 

Length p^ to m^ 37.6 mm. 

Length p< (estimated) 7.3 mm. 

w The original has "m^", an obvious misprint. — O. Q. S. 



182 BULLETI]N' 16 9, UNITED STATES KATIOXAL MUSEUM 

Width p^ 7.5 mm. 

Length m^ 9.4 mm. 

Width m> 10.0 mm. 

Length m^ 5.5 mm. 

Width xn? 9.3 mm. 

Length of lower dental series c to nis 05.0 mm. 

Length mi to ms 28. 5 mm. 

Length m2 9.4 mm. 

Width m2 7-5 mm. 

Length ms 9.9 mm. 

Width ma 6.5 mm. 

Depth of jaw at m2 21.5 m.m. 

Depth of jaw at p2 18.2 mm. 

Total basal length of skull (estimated) 155.0 mm. 

Width of skull across orbital region, including zygomas (estimated) _ _ 65.0 mm. 

"Even in our present knowledge of the claenodont group it is diffi- 
cult to determine the limits of individual variation and species char- 
acters ; and it is quite probable that some of those here stated have a 
much wider significance than I have given them, while others may have 
less importance. This statement applies equally to the following 
more detailed description of the type specimen. 

"The skull is not greatly specialized but shows the following char- 
acteristic modifications: glenoid fossae situated forward in position as 
in the Miacidae; sagittal crest high and prominent (primitively cor- 
related with the small brain, and the large canines with which were 
doubtless associated heavy temporal muscles), occipital crest but little 
expanded ; nasals long, slightly widening forward and overlapped by a 
considerable portion of the maxillary in the normal creodont-carnivore 
way; posterior root of zygoma prominent with roof of glenoid fossae 
depressed below the level of basisphenoid plane as in the bears; rela- 
tive position and arrangement of cranial foramina, also as in the 
XJrsidae, that is, the optic foramen is placed well forward of the ante- 
rior sphenoidal fissure which lies close to the foramen rotundum, with 
the anterior opening of the alisphenoid canal just below them; the 
ethmoid foramen lies nearly above the optic foramen and well behind 
the postorbital process (an important character, as the position of this 
foramen marks the posterior border of the cribriform plate of the 
ethmoid); foramen ovale, and posterior opening of alisphenoid canal 
connected by a groove or depression which is separated from the 
basisphenoid plate by a prominent ridge of the alisphenoid." 

Discussion. — Dr. Gidley also well described and figured the various 
known limb elements of this species. As already suggested, most of 
the distinctions noted by him were based on comparison with a single 
specimen of Claenodonferox, and they disappear or seem of very little 
importance when more material is brought into the comparison. The 
proportionate widths of radial facets on scaphoid and lunar are 5.3:8.1, 



FORT UNIOjST OF CRAZY MOUNTAIN FIELD, MONT. 



183 



or 0.65 (almost exactly two-thirds, as stated by Gidley), and in one 
specimen of Cjerox (that mth which Gidley made comparisons) this 
ratio is 10.1:15.4, or 0.66, so that the different size, preservation, and 
to a slight degree proportions evidently misled his eye when he sup- 
posed the ratio to be significantly smaller in C. montanensis. The 




Figure i7.—Ctaenodon montanensis (Gidley), U.S.N.M. no. 8362, skull and jaws, left side. Three-fourths 
natural size. (After Gidley, 1919, fig. 5.) 




FiGUEK Z8.—Claenodon montanensis (Gidley), U.S.N.M. no. 8362, skull, palatal view. Three-fourths 
natural size. (After Gidley, 1919, fig. 6.) 



ratio of total widths is 0.47, or about half, as stated by Gidley, in 
C. montanensis type, and 0.46 in the specimen of C.ferox, which again 
is a wholly insignificant difference. Computation of the exact figures 
also shows Gidley's impression that the vertical depths of the anterior 
faces of these bones are relatively less than in C.Jerox to be mistaken. 
They are in fact slightly, but not significantly, greater than in this 
specimen of C. ferox. 

119212—37 13 



184 



BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



In Gidley's description of the calcaneum (1919, p. 552), "tibial face" 
is probably a misprint for "fibular facet." The type calcaneum is 
somewhat damaged in this region. A specimen collected after Dr. 
Gidley's paper was pubUshed shows that in C. montanensis the fibular 
facet on the calcaneum is relatively quite as well developed as in 
C. ferox. His statement, "cuboid with facet for the astragalus, 
navicular and ectocuneiform arranged horizontally, nearly parallel and 
merging into each other" also appears to involve a misprint or lapsus, 
since it is inconsistent with his accurate figures and is either not clear 
or not correct. As his figures show, the astragal ar facet is at an angle 
of nearly 90° to the navicular facet, and the latter and the ectocunei- 






FiGURE 39.— Oaenodon montanensis (Gidley), U.S.N.M. no. 8302, foot bones: a, Lunar and scaphoid, dorsal 
view; b, part of tarsus, dorsal view; c, parts of the three median digits of pes, dorsal view. Natural size. 
(After Qidley, 1919, figs. 7 and 8.) 

form facet are approximate!}^ in the same vertical plane. Comparison 
of several specimens of C. ferox does not confirm the supposed differ- 
ence in tliis species in the separation and different outline of the two 
last mentioned facets on the cuboid. These facets are much less 
definite in the available specimens of C.jerox ^^ than in C. montanensis, 
but differ little in outline. 

Dr. Gidley's important conclusion that the present limb bones are 
closely similar to those of Claenodon ferox is certainly correct and is 
only emphasized by these slight corrections of details. The C. mon- 
tanensis material is Uttle over half of the size of that of C. ferox, and 
it differs in details of proportion, strength of processes, or rugosities. 



»i The artist has made their outline far too distinct in Gidley, 1919, pi. 28, fig. 2a. 



FORT UXIOX OF CRAZY MOUNTAIN FIELD, MONT. 185 

such as are normally specific functions of size, but not in any essential 
structure. 

As already suggested, Dr. Gidley's comparison with Ursus seems 
to me to be beside the point and to involve no features not to be 
expected by convergence in hea\aly built plantigrades not more closely 
related than as members of wholly different groups of the same order. 

The species is surely distinct from C. Jerox, being excluded from 
that group by the smaller size, reduced hypocone of M\ and reduced, 
size and more transverse proportions of M^ (Some of the other 
characters given by Gidley are not of probable specific value.) The 
size is within the probable range of the small unnamed Torrejon 
species. For instance, the length of M2 is 9.2 in the largest Torrejon 
specimen of the small species and 9.4 in the type of C. montanensis. 
The size distribution doubtless overlaps, but were a larger series 
available it is probable that the mean for the Fort Union specimens 
would be found to be significantly greater. The reduction of the 
posterior part of M^ is also within the extreme limit of variabihty of 
the Torrejon species but probably is a specific character varying about 
a different, but not widely separate, mode. The somewhat smaller 
hypocones of M^"^ and the less conical protocone of P* seem to be 
beyond the lunits of the Torrejon specimens and thus still better 
specific characters, on present data. Possibly correlated with the 
differences in P^ is the somewhat narrower, more distinctly unicuspid 
character of P4, also apparentlj^ a good specific character.^^ 

U.S.N.M. no. 9634 is an isolated Mi from the Gidley Quarry, 
measuring 9.4 by 6.5 mm and referable to this species with Httle 
doubt. No. 6159, from Loc. 52,^^ includes right and left Mg, appar- 
ently associated, and other fragments, also referable to C. montanensis. 

CLAENODON SILBERLINGI (Gidley) 

Figure 40 
Neodaenodon silberlingi Gidley, 1919, p. 552. 

Type.— U.S.N.M. no. 8363, part of left^" maxilla with P^-M^ and 
alveoli for canine and P^"^. Collected by Dr. J. W. Gidley. 

Horizon and locality. — Gidley Quarry, Fort Union, Middle Paleo- 
cene horizon, Sweetgrass County, Mont. 

Diagnosis. — Gidley (1919, p. 553): "A slightly smaller species than 
N. montanensis from which it differs as follows: cusps of all the molars 
seemingly^ more depressed; m^ and pm's^'* somewhat less reduced 

M These, of course, substantiate the validity of the still unpublished Torrejon species, rather than of C. 
montanensis, which has priority and is surely distinct from any species previously named. 

83 Labeled '"Gidley Qu.' (Recorded Loc. 'No. 52' = Loc. No. 4)." Loc. 52 Is very near the Gidley Quarry 
and about 50 feet lower stratigraphically. The difference does not appear to have any importance, but 
the localities are not exactly the same. 

s* "Right" in the original designation of type (Gidley, 1919, p. 552) is a lapsus. 

"' Though found in its original bed, the enamel of all the teeth is considerably damaged through weather- 
ing or leaching by surface water which had reached the specimen through cracks in the matrix." 



186 



BULLETIISr 16 9, UNITED STATES NATIONAL MUSEUM 



although more reduced than in Claenodon: all the cheek teeth, ex- 
cept p^, relatively wider; distance between p^ and the canine relatively 
greater indicating a somewhat more elongate face ; infraorbital foramen 
approaching nearer to the alveolar border above p^. 

"This species in size approximates C. protogonioides (Cope) but is 
apparently clearly distinguishable from the Puerco species by the 
much greater reduction and more oval contour of m^, and in the 
relatively wider proportion of all the cheek teeth. 

"Measurements of A'', silberlingi 

c to m^ 60.0 mm, 

p3 to m* 34.5 mm. 

m* to m* 21.4 mm. 

ml length 7.0 mm. 

m' width - 8.8 mm. 

m^ length - 7.4 mm. 

m^ width 11.5 mm. 

m^ length 5.0 mm. 

m^ width. 9.0 mm. 

Distance between p^ and p^ 5.0 mm. 

Height of p' (outside) ._ 5.5 mm. 

Length of canine alveolus — 7.5 mm." 




Figure 40,- 



-Claenodon silberlingi (Qidley), U.S.N. M. no. 8363, left upper jaw: a. Crown view; 6, external 
view. Natural size. (After Qidley, 1919, fig. 9.) 



Discussion. — Allusion to "C. proiogonioides" implies comparison 
rather with the unnamed Torre j on species of Claenodon than with 
the different Puerco species to which the name properly appUes. 

The type of this species is so poor, the cusp structure being very 
much obscured and in part destroyed by corrosion and breakage, that 
it cannot surely be distinguished from the small Torrejon species, on 
one hand, or from C. montanensis, on the other, although these two 
are distinct from each other. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 187 

The relative size and contour of M^ are, in fact, well within the 
range of variation of the Torrejon species, and the teeth are not 
significantly more transverse. The size is large for that species but 
not beyond its presumable range and hence of doubtful significance. 
It is impossible to give good clear diagnoses separating the two, 
although it is my opinion that they are probably distinct. 

It is, on the other hand, probable that C. silberlingi is synonymous 
with C monianensis (adding to the probability that it is not the same 
as the Torrejon species). The size is about the same, and both types 
are from one quarry. M^ is a little shorter in C. silberlingi, and some- 
what more transverse, but these are doubtfully real, since the speci- 
men is so poorly preserved, and if real are not marked enough to prove 
any taxonomic distinction. M^ is definitely larger than in C. mon- 
ianensis. The ratio of their lengths, the dimension in which they 
differ most, is 1.10. In Torrejon specimens of the C.jerox group the 
variation in absolute dimensions is much greater than this, and the 
size of M^ relative to M^ or IVP also varies quite as much as the differ- 
ence between C. silberlingi and C. monianensis, although this is a more 
constant figure. 

The distance between P^ and the canine is almost exactly as in C. 
monianensis. In calling it "relatively greater", Gidley must have 
meant relative to the length of M\ but as the other tooth dimensions 
are as great as in G. monianensis this is simply to repeat that the 
length of A'l^ is relatively small and is not a character of the diastema. 
M^~^ may have had larger hypocones than in C. monianensis, but this 
is almost hypothetical, and the protocone of P* may have been stronger, 
also rather dubious. 

I retain the name tentatively, on these very doubtful characters, 
but beUeve that the species will probably prove to be invahd. 

CLAENODON LATIDENS (Gidley) 

Figure 41 
f Neoclaenodon latidens Gidlet, 1919, p. 554. 

Type. — U.S.N.M. no. 8388, right lower jaw with M2-3, a small 
fragment of Mi, and the broken lower part of the ramus from the 
canine alveolus to the angle. Collected by Dr. J. W. Gidley. 

Horizon and localiiy. — Gidley Quarry, Fort Union, Middle Paleocene 
horizon, Sweetgrass County, Mont. 

Diagnosis. — Gidley (1919, pp. 554-555): "Size approximately that 
of N. monianensis, but wdth decidedly wider molars; jaw relatively 
longer, much straighter, and more slender. Since the upper dentition 
of A^. latidens and the lower dentition of N. silberlingi are not known, 
these species can not now be compared, but the difference in size, 
seems sufficient to distinguish them. 



188 



BULLETII^ 16 9, UNITED STATES NATIONAL MUSEUM 



"Measurements 

Length of ma 9.7 mm. 

Width of ma 8.4 mm. 

Length ma 9.6 mm. 

Width of ms 7.6 mm. 

Depth of jaw atm2 -- 16.0 mm. 

"Unfortunately, as in the type of A^. silberlingi, the enamel of the 
molars has been considerably damaged through weathering or leach- 
ing by surface water, which somewhat obscures the detailed structure. 

''The generic reference is provisional, since certain features, as the 
straight and more slender proportions of the jaw and relatively greater 
width of the lower molars, so sharply distinguish A^. latidens from all 
other species of this genus or of Claenodon. They suggest that its 
afl&nity to the group to wiiich I here assign it may be, after all, not very 
close. More complete and better preserved material may, therefore, 
necessitate placing it in a distinct genus." 




a 




FiGURK a.— Claenodon latidens (Gidley), U.S.N.M. no. 8388, with parts in outline probably adapted from 
other species nf Claenodon, risht lower jaw: a, Crown view; 6, external view. Natural size. (After Gidley, 
1919, fig. 10.) 



Discussion. — The apparent differences from C. montanensis in the 
shape of the mandibular ramus are, in my opinion, illusory and due to 
the different preservation of the two specimens. The jaws appear to 
have been almost identical or at least well witliin the possible range for 
a single species. So far as available material goes, the species depends 
wholly on the notably wider M2_3. That this is of specific value is not 
certain, especially as the size is otherwise that of C. montanensis and 
both are from the same quarry, but the species may be tentatively 
retained. I see no reason to suspect that a new genus is represented. 



FORT U2^'I0X OF CRAZY MOUNTAIN FIELD, MONT. 189 

CLAENODON VECORDENSIS Simpson 

Figure 42 

Claenodon vecordensis Simpson', 1935d, p. 232. 

Type.— U.S. 'NM. no. 13781, left AP-^. Collected by A. C. Silber- 
ling and G. G. Simpson, 1932. 

Horizon and locality. — Loc. 9, 300 feet above the base of Fort Union 
No. 1, Crazy Mountain Field, Mont. 

Diagnosis. — M^ similar to that of C. silberlingi in outline but 10-20 
percent larger and somewhat more transverse; hypocone vestigial, 
strong crenulated internal cingulum. M^ relatively as large as in 
C.ferox and similar in structure except for smaller metacone and more 
evenly rounded external border; vestigial hypocone present. 

Discussion. — This species is smaller than the smallest IvQown variants 
of C. ferox, has a smaller hypocone on M^, and the contours of M^ 
and M^ are different and beyond the known range of variation of that 
species. C. silberlingi is somewhat smaller and has different tooth 
proportions. M^ is much larger and less transverse than in C. mon- 
tanensis and has the posterior part better developed. The small 
unnamed Torre j on species is much smaller and has less wrinkled 
enamel, and the internal cingulum is feebler or absent. 




FrGURE i2.— Claenodon 
vecordensis Simpson, 
U.S.N.M. DO. 13781, left 
M2-3, crown view. Nat- 
ural size. 




Figure i3.—'! Claenodon 

sp., U.S.N.M. no. 6158, 

left Ml, crown view. 

Natural size. 



It is unfortunate that another poorly known species must be added 
to this genus, already burdened with several species of doubtful status, 
but the present specimen is identifiable and surely cannot enter into 
any species previously established so far as their range of variation is 
known or can be fauiy inferred. It is, furthermore, from a very dif- 
ferent geological horizon from the other Fort Union claenodonts and 
one from which little material has been obtained, so that its strati- 
graphic importance also necessitates some convenient designation for it. 

Measurements: Length M^, 9.0; width M^, 13.5; length M^, 6.7; 
width M\ 10.0. 

7CLAENODON species 

Figure 43 

U.S.N.M. no. 6158, from the Gidley Quarry, is a left lower jaw frag- 
ment with Ml. Among Dr. Gidley's notes are two sheets devoted to a 



190 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

description of this specimen, in which it is placed in a new species. 
Apparently it was at first placed in Claenodon with a query, and later 
the generic name was erased and another, which appears to be new, 
substituted, but no corresponding change was made in the description, 
and the genus was not defined. I do not believe this to be adequate 
for the definition of either genus or species and feel obliged to suppress 
these manuscript names. The specimen is aberrant (with respect to 
species of Claenodon) in several details, but their significance cannot be 
judged and comparative Fort Union material is too scanty for good 
diagnosis. It is, for instance, entirely possible that this belongs to 
Claenodon latidens.^^ 

Genus DEUTEUOGONODON Simpson 

Deulerogonodon Simpson, 1935d, p. 232. 

Type. — D. montanus (Gidley). 

Distribution. — Middle Paleocene, Fort Union, Montana. 

Diagnosis. — Dentition basically arctocyonid in type, and resembling 
Protogonodon and Claenodon. Small, distinct, cingulum hypocone on 
M^~^ (at least), cingula almost completely circling these teeth. Sm.all 
but well-defined mesostyle present. Parastyle of M^ a distinct cusp, 
crowning a lobe projecting strongly externally. Lower molars with 
trigonid only slightly higher than talonid, metaconid smaller than but 
as high as protoconid. Paraconid very small but distinct, subconical, 
on slope of metaconid directly anterior to its apex. Talonid basin 
open, crescentic lophid continuous but crest differentiated into hypo- 
conid, hypoconulid, and entoconid, progressively smaller in that order. 
Enamel wrinkled, but all cusps clear-cut and little or no tendency to 
form crenulations or accessory cuspules. 

Discussion. — This seems to be a very distinctive genus, at once 
distinguished from any similar form by the presence of a mesostyle. 
The combination of the other characters given is equally distinctive, 
although individually they are less so. The genus could be a deriva- 
tive of Protogonodon, although it is too incompletely known and too 
distinctive to establish this as a definite theory. I know of no Torre- 
jon genus that compares more closely than the probably related but 
manifestly distinct Claenodon, and none of the lower Eocene arctocyo- 
nids could be derived from Deuterogonodon. The possibility that 
Phenacodus was derived not from Tetraclaenodon, as commonly sup- 
posed, but from Protogonodon by way of a form something like Deu- 
terogonodon is worthy of consideration but cannot be very seriously 

»« Dr. Qidley may have had the same idea, and his manuscript is perhaps older than the publication of 
1919. The specimen was collected before the type of C. latidens and was obviously in Dr. Oidley's hands 
when he wrote his claenodont paper, so that its omission may well be due to his having decided that the 
specimen did not warrant a new name. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



191 





upheld on present evidence. Aside from the presence of a mesostyle, 
Deuterogonodon is much less like Phenacodus than is Tetraclaenodon.^^ 
Dr. Gidley's manuscript notes include two drafts of a description of 
the type of this genus, in both of which it is referred to Protogonodon. 
On one, however, almost surely the second, the words "new genus" 
have later been written under "Protogonodon." Gidley thus came to 
recognize the clear-cut distinction of this genus from Protogonodon, but 
his notes do not contain any generic diagnosis 
or new generic name, and I have been forced to x3% /^i' 

supply these. 

DEUTEROGONODON MONTANUS (Gidley) %mW M 

Figure 44 NSm.- 

a 

Deuterogonodon montanus (Gidley) Simpson, 1935d, p. 233. 

Type.—U.S.'NM. no. 6160, part of right maxilla /0^:f^:'fM 

with a fragment of M^, M^ lacldng the paracone 
and parastyle, and M'^ complete, mth a left lower 
jaw fragment, possibly of the same individual and 
almost surely of the same species, with the talonid u 

of Ml and most of M2. If these should prove not 
to be one individual, the upper teeth constitute 
the type, and the lower teeth are a para type. &^ 

Collected by A. C. Silberling. 

Paratype. — U.S.N.M. no. 6161, isolated right Mg. 

Horizon and locality. — All material is from Loc. \ j , / 

25, about 300 feet above the base of Fort Union ^ 

No. 2, Sweetgrass County, Mont. fiqvre n.-Deuterogonodon 

Diagnosis.— Gidley: "Somewhat larger than P. montanus (Gidiey): a, u.s. 

rx^ 7 1 /^ N ,, fi7 N.M. no. 6160, right M»-», 

[Protogonodon] pentacus (Cope). ^^ crown view; b, u.s.n.m. 

Simpson: Sole known species of the genus as °°- ^i*^^- "^^^ ^'' ^"''^^ 

^ view; b', same, internal view. 

denned above. Natural size. 

Measurements are as follows: 

M2 median width 14. 6 

M3 length 10 

M2 (paratype) width 10. 5 

M2 (paratype) length 12. 6 

8' A new species of Protogonodon from the Puerco, which I have described in a note published as a 
supplement to Matthew's Paleocene Memoir, suggests that within the genus Protogonodon there was a 
tendency to develop along two different lines, one leading (or related and collateral) to Tetrnctaenodon and 
one more definitely creodont and ClaenodovAike. If derived from Protogonodon, Deuterogonodon probably 
arose from a species of the latter, rather than of the former, group. 

8' I quote only enough of Dr. Gidley's diagnosis to establish his authorship of the species. The rest of 
the diagnosis compares with the Puerco species of Protogonodon and is hence rather generic than specific, 
end among the few characters given I cannot agree as to the reality or value of some, and others seem to 
Involve slips of the pen that I cannot correct with any certainty that Dr. Gidley's thought is being followed. 
The rough manuscript was far from completion. 




192 BULLETIN 16 9, UXITED STATES NATIONAL MUSEUM 

7DEUTEROGONODON species 

U.S.N.M. no. 9653 includes part of a left maxilla with P*-M' 
and part of a right mandible with the heel of M3. All the teeth are 
incomplete and much battered, and none is directly comparable with 
the types of D. montanus, so that pertinence to that genus and species 
cannot be established but is probable, at least as far as generic 
identity .^^ The principal characters exliibited are that P* has a strong 
conical protocone, somewhat smaller than the external cusp or cusps, 
and that in the talonid of M3 the three cusps, especially the entoconid, 
are more distinctly separated than in Mi_2 of the type of D. montanus. 
These specimens are from Loc. 18, the horizon of which is in doubt 
but is higher than that of the types of D. montanus and in Fort 
Union No. 3. 

There are likewise a few tooth and limb fragments, from the type 
locality, that probably belong to this genus but are of no particular 
value at present. 

Subfamily Oxyclaeninae Matthew, 1937 (Oxyclaenidae Scott, 1892) 

The oxyclaenine genera of this fauna, Metachriacus, Mimotricentes, 
Spanoxyodon, Prothryptacodon, and (somewhat doubtfully) Chriacus^ 
belong with several other Paleocene genera in a very confusing com- 
plex. The size ranges of their species do not differ greatly, and their 
morphology is markedly stereotyped in general pattern. Within the 
Hmits of this general type, however, they seem to ring almost eveiy 
possible change in combinations of detail, so that they are difficult 
to distinguish yet are amazingly varied in minutiae and cannot be 
grouped into one or a few broad but natural genera. The variations 
involve, among other features: 

1. Placing of the canine (from vertical in Tricentes, etc., to strongly 
procumbent in Prothryptacodon, etc.). 

2. Number and crowding of premolars and associated develop- 
ment of diastemata, varying from such types as Metachriacus to 
Spanoxyodon. 

3. Molarization of P4, from a wholly premolariform type, as in 
Tricentes (and several other genera) to a submolariform condition as 
in Spanoxyodon. 

4. Reduction of the paraconid, from strong and distinct (e. g., 
Deltatherium) to almost indistinguishable (e. g., M2-3 oi Metachriacus). 

5. Placing of the paraconids, from almost strictly internal (e. g., 
Mimotricentes) to almost strictly median (e. g., Tricentes). 

6. Elevation of the trigonids and their shearing character, from 
high and strongly shearing (e. g., Chriacus) to low and bunodont 
(e. g., Tricentes). 

" Dr. Gidley labeled them as of the same species. 



FORT UNION OF CRAZY MOUNTAIN" FIELD, MONT. 



193 



7. Proliferation of accessory cuspules, from practically nil (e. g., 
Chriacus) to considerable and distantly approaching the multicuspid 
"arctocyonines" (e. g., Metachriacus). 

8. Development of hypocones on upper molars from practically 
nil (e. g., Deltatherium) to pronounced (e. g., Chriacus). 

Other characters, known in fewer genera, also seen to be highly 
distinctive, such as the molarization of upper premolars, width of 
external upper molar shelf, shape of paracone and metacone, and 
many other characters. 

Table 38 contrasts the genera of this complex that occur in this 
fauna, and those most likely to be confused with them, as regards 
these characters. 



Table 38. — Comparison of dentition characters in six genera of Oxyclaeninae 



Genus 



Chriacus.. 

Metachriacus... 
Trkentes 

Minwtricentes . . 
Spanoxyodon... 

Prothryptacodon 



Canine 



Moderately procum- 
bent. 

Cf. Chriacus 

Crown vertical 

Cf. Tricentes 

Cf. Chriacus 



Strongly procumbent, 
root extending be- 
neath premolars. 



Present. 



.do. 



Pi absent.. 

Present 

Pi-2 absent- 
Present 



Diastemata 



Slight or none 

Cf. Chriacus 

Short, C-P2.. 

None 

Long, C-Ps 

Very slignt, around 
Pi, P2. 



P4 



Slender, with small, dis^ 

tinct metaconid. 
Cf. Chriacus. 
Stouter, no metaconid. 
Cf. Tricentes. 
With metaconid larger 

than in Chriacus. 
Slender, metaconid 

barely incipient or 

absent. 



Genus 


Paraconids of M2-J 


Trigonids of Mi_3 


Cuspules of Mi-3 


Mi-3 


Chriacus.. 


Distinct, near meta- 


Elevated, shearing. 


No accessory cus- 


With well-developed. 




conids, internal. 




pules. 


hypocones, some- 
tendency to devel- 
op protostyles 


Metachriacus 


Vestigial, placed 


Lower than in 


Tendency to de- 


Sharp cingulum 




about as in Chri- 


Chriacus, still 


velop cuspules on 


around protocone3 




acus or slightly 


shearing. 


anterior rim of 


of Mi-3 but hypo- 




less internal. 




trigonid, conules 
onbothhypoconid 
wings, and slight 
metastylid. 


cones rudimentary 
on M2, absent^on 
M3, no distinct 
protostyles. 


Tricentes 


Vestigial, low on 


Still, lower, buno- 


Enamel rugose or 


Hypocones small or 




crown, nearly me- 


dont. 


papillated but few 


absent, no proto- 




dian. 




or no definite cus- 
pules. 


styles. 


Mimotricentes 


Vestigial, higher on 
crown than in 
Tricentes and in- 
ternal. 


Cf. Tricentes 


Cf. Tricentes 


Cf. Tricentes. 


Spanoxyodon 


About as in Chriacus 
or slightly less in- 
ternal. 


About as in Chria- 
cus or slightly 
lower. 


Cf. Cliriacus 


(Unknown.) 


Prothryptacodo n.. 


Comparable to Me- 


Cf. Chriacus 


Cf. Chriacus 


(Unknown.) 




tachriacus, but 
slightly better 
differentiated. 









194 



BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



Renewed study has necessitated some modification of the arrange- 
ment given in a preUminary paper (Simpson, 1935d). In the first 
place the species there called Chriacus pusiUus was wrongly placed in 
Chriacus, It belongs in Metachriacus , where it is indistinguishable 
from the genotype, M. punitor. This makes possible some redefini- 
tion of Metachriacus, which proves to be even more distinct from 
Chriacus than was at first supposed. The species called Tricentes 
latidens (quoted from Dr. Gidiey's notes) is now seen to be distinct 
from Tricentes, despite a very marked adaptive resemblance, for it has 
Pi, apparently always absent in Tricentes, and the paraconids are in 
quite a different position although reduced about as in Tricentes. It is 
necessary to erect a new genus for this species, since redefinition of 
Tricentes to include it would make that genus so broad as to destroy 
all balance in the generic arrangement of the family achieved by 
Matthew and others. 

Spanoxyodon is a peculiar type with aberrant speciahzation, and 
Prothryptacodon is evidently a very primitive form slightly but de- 
finitely modified in the direction of Thryptacodon. 

For convenience in identifying fragmentary material a summary 
(table 39) of lower tooth dimensions is here given. 

Table 39. — Measurements (in mm) of loiver dentition in seven species of 

Oxyclaeninae ' 



Species and number of specimens 


P* 


Ml 


Mj 


Mj 


L 


W 


L 


W 


L 


W 


L 


W 


Prothryptacodon furens (2) 


4.9 


2.7 


5.2 
7.1 
4.7 
5.4 
5.2 
5.6 
4.8 


3.7 
5.9 
3.7 
4.2 
3.9 
4.7 
3.6 


5.2 

5.0 
5.8 
5.8 
6.0 
5.6 


4.2 

4.3 
4.9 
4.5 
5.5 
4.6 


5.3 

5.7 
6.7 

6.1 
5.5 


4.0 


^ Chriacus pugnax (1) 






4.3 
5.0 
5.0 
5.4 
4.4 


2.7 
2.9 
2.8 
3.9 
3.0 


3.7 


Metachriacus prococator (12) 


4.1 






Mimoiricentes latidens (2) 


4.7 


Mimotricentes angustidens (4) 


3.6 



1 The figures in this table are means for the number of specimens (in all, not necessarily for every dimen- 
sion) shown in parentheses. The range of variation is known reasonably well only in Metachriacus punitor 
and M. provocator, as given hereinafter. The dimensions in themselves are not necessarily distinctive, for 
instance between Metachriacus provocator and Spanoxyodon latrunculus, but in such cases there are, of 
course, well marked nonnumerical distinctions. Some worn and incomplete specimens might, however, 
be unidentifiable in such cases. 

Genus PROTHRYPTACODON Simpson 

Pr othrT/ptacodon Simpson, 1935d, p. 233. 

Type. — Prothryptacodon jurens Simpson. 

Distribution. — Middle Paleocene, Fort Union, Montana. 

Diagnosis. — Canine semiprocumbent, root extending beneath pre- 
molars, as in Thryptacodon. Pi -2 spaced widely. P4 similar to 
Thryptacodon. Molar trigonids higher than in Thryptacodon, para- 



FORT UXIOX OF CRAZY MOUNTAIN FIELD, MONT, 195 

conids reduced and in nearly the same position as in Thryptacodon but 
more distinct, higher on crown, trigonids less basined, and with fewer 
accessory cuspules. Only one distinct inner talonid cusp (entoconid), 
as opposed to two in Thryptacodon. 

Discussion. — This genus could well be ancestral to Thryptacodon 
and in any case is evidently allied to it. The adaptive characters are 
somewhat intermediate betv»'een the more primitive types, such as 
Oxyclaenus, and the more complex type seen in Thryptacodon, involv- 
ing some flattening of the molar crowns and proliferation of cuspules. 
In these characters Thryptacodon and to a less extent Prothryptacodon 
parallel or converge toward the Claenodon-Anacodon hne. The latter 
group, how^ever, is much earlier and more highly specialized in this 
rather bearlike direction. Prothryptacodon is contemporaneous with 
Claenodon in the Middle Paleocene, and Claenodon is already more 
specialized than Thryptacodon in this direction. Thryptacodon 
appears in the Upper Paleocene and survives into the lower Eocene, 
where Anacodon appears as a highly aberrant survivor of the Claenodon 
group. 

The canine is slender, laniary, compressed, with the root con- 
siderably larger than the crown and meeting the latter at an angle of 
about 135°. The root is implanted almost horizontally and extended 
at least to the anterior end of Po. Pj, from its alveolus, had a single 
root and was well spaced, slightly nearer to the canine than to P2. 
Pa and P3 were 2-rooted, and P2 is preceded and followed by a short 
diastema. P4 has a very slight internal swelUng, high on the crown, 
that may indicate an incipient metaconid. In one specimen M2 has a 
faint external trigonid cingulum, and in another this is more definite. 
There are two mental foramina, one beneath Pi and one beneath P3 
or the anterior end of P4. The other characters of genus and species 
are adequately given in the diagnosis and figures. 

PROTHRYPTACODON FURENS SimpsoB 

FiGUBE 45 

Prothryptacodon furens Simpson, 1935d, p. 234. 

Type. — U.S.N.M. no. 9260, right lower jaw with P4-M3 and 
alveoli. Collected by A. C. SilberUng. 

Horizon and locality. — Gidley Quarry (referred specimen from 
Silberling QuarrjO, Fort Union, Middle Paleocene horizon, Crazy 
Mountain Field, Mont. 

Diagnosis. — Sole known species of genus. Measurements in 
table 40. 

Remarks. — Only two specimens are as yet known, both partial 
lower jaws. U.S.N.M. no. 9262 is from the Silberling Quarry. 



196 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

Table 40. — Individual measurements (in mm) of Prothryptacodon furens 



Specimen 


P4 


Ml 


Ma 


Ml 


L 


W 


L 


W 


L 


W 


L 


W 


Type 


4.9 


2.7 


5.2 


3.7 


5.2 
5.1 


4.2 
4.2 


6.3 


4 


U.S.N.M. no. 92fi2 


















FiGURK 45. — Prothryptacodon furens Simpson, U.S.N.M. no. 9260, right lower jaw: a. Crown view; 6, 
internal view. Twice natural size. 




Figure i6.—Chriacus pugnax Simpson, U.S.N.M. no. 13782, right lower jaw, crown view. Twice natura 

size. 



Genus CHRIACUS Cope, 1883 

This genus typifies the Torrejon but has been reported also in the 
Puerco and in the Almagre. It is improbable that a single genus had 
this enormous, almost unique length of distribution, and the earliest 
and latest forms, known only from fragments, may well prove to be 
distinct. The pattern is a simple and generalized one, easily confused 
with that of allied forms, and requiring close study and good material 
for its certain distinction. 

The appearance of Chriacus in the present fauna would be expected, 
from its age relationships, and this genus was reported by Douglass 
(1908) and by me (1935d). The earlier reports, howeve/ now prove to 
be doubtful or erroneous. As elsewhere noted, one species hitherto 
referred to Chriacus is now placed in Metachriacus. The other, 
C. pugnax, is retained here, but the specimen on which it is based is so 
incomplete that the generic reference is not certain. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 197 

CHRIACUS PUGNAX Simpson 

Figure 46 
Chriacus pugnax Simpson, 1935d, p. 235. 

Type. — U.S.N.M. no. 13782, right lower jaw with Mi_2 and alveoli. 
Collected by A. C. Silberling and G. G. Simpson. 

Horizon and locality. — Loc. 78, Fort Union, Crazy Mountain Field, 
Mont. 

Diagnosis. — About the size of C. pelvidens, but molars wider, tri- 
gonids less elevated, talonids of Mi_2 notably wdder than trigonids. 
Ml length 7.1, trigonid width 4.9, talonid width 5.9. 

Remarks. — In addition to the characters cited in the diagnosis, there 
is a diastema anterior to P3 in the unique specimen, but the length and 
significance of this cannot be established. The specimen is from one of 
the lowest horizons that have yet yielded mammals in this field, only 
200 feet above the base of the Fort Union No. 1. This suggests 
comparison with Mimotricentes angustidens, also from a low (but not 
such a low) horizon, but the latter is markedly smaller and otherwise 
less ChriacusASkQ. 

Genus METACHRIACIJS Simpson 

Meiachriacus Simpson, 1935d, p. 235. 

Type. — Meiachriacus punitor Simpson. 

Distribution. — Middle Paleocene, Fort Union, Mont. 

Diagnosis. — Canine and premolars about as in Chriacus. Molar 
trigonids lower than in Chriacus but still shearing rather than bunodont 
(as in Tricentes). Paraconids reduced and poorly distinguished, near 
metaconids, placed about as in Chriacus or slightly less internal. 
Accessory cuspules developing on anterior rim of trigonid, on hypoconid 
wings, and a slight metastyhd. Upper molars with sharp cingulum 
around the protocone, but no protostyle. Hypocone present on M^, 
rudimentary or indistinguishable on M^, and absent on M^. 

Remarks. — This genus is hardly distinguishable from Chriacus on 
the basis of the premolars, which distinguish it from almost all other 
known genera, but the molars are of quite a different adaptive type, 
the lower crowns, blunter cusps, and prohferation of accessory cus- 
pules in the lower molars representing convergences in varying degree 
toward Tricentes and toward Claenodon. 

METACHRIACUS PUNITOR Simpson 

Figures 47-49 

Meiachriacus punitor Simpson, 1935d, p. 235. 

Chriacus pusillus Simpson, 1935d, p. 234. 

Type.— U.S.N.M. no. 9288, left lower jaw with Mi_3. Collected by 
A. C. Silberling. 



198 BULLETIN 16 9, Ui^iTED STATES NATIONAL MUSEUM 

Paratype.—V.S.^M. no. 9286, right lower jaw with P3-M3 (Mi and 
M3 broken). Collected by A. C. Silberling. 

Type o/Chriacus pusillus.— U.S.N.M. no. 9270, right lower jaw with 
P2-M2. Collected by Dr. J. W. Gidley. 

Horizon and locality.— Gidley and SilberHng Quarries, Fort Union, 
Middle Paleocene horizon, Crazy Mountain Field, Mont. 





Figure il .—Mdachnacm punitor Simpson: a, L'.S.N.M, no. oa^S, left Mi_3 crown view; 6, U.S.N.M. no. 
9286, with parts in outline from nos. 9282 and 9486, right lower jaw, external view. Twice natural size. 




Figure i&.—Meiachriacus punitor Simpson, small variation, U.S.N.M. no. 9270, right lower jaw, internal 

view. Twice natural size. 




Figure i'd.—Metachuacus punitor Simpson, U.S.N.M. no. 9331, left M'-', crown view. Four times natural 

size. 



Diagnosis. — Heel of P4 expanded, basined, squarely truncated pos- 
teriorly. Molar crenulation moderate. Mi_2 less wedge-shaped. 
Measurements given in tables 42 and 43. 

Discussion. — My earlier publication on the two species here united 
was confused and incorrect. By a misinterpretation of a small worn 
specimen and by the acceptance of an incorrect association, I was led 
to place a few of these specimens in Chriacus and therefore I did not 



FORT UNIOIST OF CRAZY MOUNTAIN FIELD, MONT. 



199 



properly compare them with the better matericals manifestly belonging 
in a distinct genus, named Metachriacus. With the removal of the 
extraneous material and renewed comparison of a large number of 
specimens, it is clear that Metachriacus punitor and "Chriacus pusillus" 
both belong in Metachriacus. The specimens previously referred to 
"Chriacus pusillus" are smaller than those placed in Metachriacus 
punitor, and M3 is slightly more reduced. Nevertheless, with recog- 
nition that they are congeneric and in view of the fact that all are 
from one horizon and locality it appears that no sharp division 
between the small and large specimens can be made and that they 
are merely individual variants of one species. This is borne out by 
the statistical constants given below. 

Of Ii-Pi only the alveoli are Imown. Judged from these, there 
were three small, subequal, closely crowded incisors, the canine was 
moderately enlarged and procumbent (but less so than in Prothrypta- 
codon), and Pi was a small tooth implanted vertically by a single 
root, P2_3 are similar, but P3 is larger. Both are slender, 2-rooted, 
pointed teeth, the outer face convex, with a sharp anterior crest and 
the posterior and anterointernal faces excavated. There is a small 
barely cuspidate heel and a tiny anterior basal cuspule. P4 is con- 
siderably longer than P3 although barely higher. The anterior cuspule 
is more distinct and the talonid much more developed, its internal 
half basined. There is a high rudimentary metaconid, not well differ- 
entiated from the protoconid, closely similar to that of Chriacus. 
The lower molars are of generalized arctocyonid type except for the 
special characters already listed. 

The symphysis is shallow, weak, and unfused, the horizontal ramus 
long and slender, the mental foramina beneath Pi and P3. 

Upper teeth have not been found associated with lower jaws of 
Metachriacus punitor, but there are several isolated upper teeth and 
jaw fragments, including representatives of the three upper molars, 
that are from the same level and locality, are harmonious in size and 
structure, and may be referred to this species with some assurance. 
In outline they closely resemble Chriacus but are distinguished by the 
entire absence of a protostyle and the considerably lesser development 
of the hypocone. 

Table 41. — Individual measurements {in mm) of Metachriacus punitor 



U.S.N.M. no. 


Pa 


P3 


P4 


Ml 


Mj 


Ml 


L 


W 


L 


W 


L 


W 


L 


W 


L 


w 


L 


W 


9288 














4.7 
4.9 


3.9 
3.9 
3.7 


4.9 
5.2 
5.0 


4.4 
4.4 
4.3 


6.0 


3.8 


92S6 










ea. 4. 1 
4.4 


2.9 
2.6 




9270 


2.8 


1.6 


3.5 


2.0 









119212—37- 



-14 



200 



BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



Measurements of the three principal spedmens and statistical con- 
stants of the whole series are given in tables 41 and 42 (see also fig. 4). 

Table 42. — Numerical data on lower dentition of Metachriacus punitor 



Variate 


N 


R 


M 


a 


V 


LP4 


6 
6 
5 
8 
8 
9 
6 
6 


4. 1-4. 7 

2. 4-3. 
4. 4-4. 9 

3. 5-3. 9 

4. 6-5. 4 

4. 1-4. 5 

5. 1-6. 1 
3. 6-3. 8 


4. 32 ±0. 08 

2. 72 ± 0. 08 
4. 66 ±0. 07 
3.'71±0. 05 
4. 98 ±0.09 

4. 31 ±0. 04 

5. 72±0. 14 

3. 68 ±0. 04 


0. 20 ±0.06 
0. 20 ±0.06 
0. 16 ±0. 05 
0. 16 ±0. 04 
0. 27 ±0.07 
0. 11 ±0. 03 
0. 35±0. 10 
0. 09 ±0.03 


4. 5 ± 1. 3 


WPi 


7. 5 ± 2. 2 


LMi 


3. 5±1, 1 


WMi 

LM2 


4. 1 ± 1. 

5. 4±1. 3 


WM2 

LM.1 

WM3 


2. 6±0. 6 
6. 2±1. 8 
2. 4±0. 7 



Three specimens from the Silberling Quarry, all very incomplete, 
are referred to this species. Each is somewhat aberrant but not 
consistently among the three and not beyond the established range of 
variation. They are not included in the figures in table 42, which are 
based on a pure sample from the Gidley Quarry. 

METACHRIACUS PROVOCATOR Simpson 

Figures 50-52 
Metachriacus provocator Simpson, 1935d, p. 235. 

Type.— U.S. '^M. no. 9278, left lower jaw with P4-M3. Collected 
by Dr. J. W. Gidley. 

Horizon and locality. — Type from Loc. 51, referred specimens from 
Locs. 81, 50, 25, 24 (all below Gidley Quarry), Fort Union, Middle 
Paleocene horizon. Crazy Mountain Field, Mont. 

Diagnosis. — Heel of P4 less expanded, httle or not basined, more 
pointed posteriorly. Molars markedly crenulated. Mi_2 more 
wedge-shaped, i. e., talonids markedly wider than trigonids. Slightly 
but significantly larger than M. punitor in most dimensions (see 
table 43). 

Discussion. — This species was originally based on three specimens 
(Simpson, 1935d), but since then five more, less complete, have been 
identified in the National Museum collection, and 10 have been col- 
lected for the American Museum, so that it is now one of the best- 
known species in the fauna. It does not occur in the quarries, where 
it is replaced by the allied but certainly distinct M. punitor, but occurs 
at the widely scattered Locs. 24, 25, 50, 51, and 81 (specimens from 
25 and 81 only in the American Museum, but used in this study), all 
of which are somewhat below the quarries, although all in Fort Union 
No. 2. Both upper and lower jaws are known from each locality. It 
is probable that the distribution, below the quarry levels, is accidental, 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



201 



that is, that M. provocator is not a significantly older species replaced in 
time by M. punitor, but that they may well have been really contem- 
poraneous but living in different facies. 

In addition to the characters cited in the diagnosis, the two speci 
mens of M. provocator that show the alveoli of Pj had this tooth 
relatively more reduced than in M. punitor, with more definite diaste- 
mata before and behind it. 

The upper molars, well known in this species, have the hypocones 
more definite and more projecting internally than in M. punitor, and 
M^ is less reduced and less transverse. There is also a tendency to 
develop a rudimentary protostyle on M^. These characters make the 
upper teeth closer to Chriacus than are those of M. punitor, and the 
upper dentition of M. provocator would not perhaps in itself be sepa- 
rated generically from Chriacus, but its lower dentition shows the 
generic characters even more clearly than does that of M. punitor. 

There are three lower and three upper jaws, some associated, from 
each of Locs. 25 and 51, three lower and one upper from Loc. 81, two 
lower and one upper from Loc. 50, and one lower and one upper from 
Loc. 24. Deviations exist, of course, between the material from dif- 
ferent localities, but these are not consistent and are not statistically 
significant. The samples are too small to demonstrate racial dif- 
ferences, if such exist. In fact the whole combined sample does not 
exceed the variety usual in a homogeneous species but on the con- 
trary shows unusually small variation, as shown by the figures in 
table 43 (see also fig. 4). 

Table 43. — Numerical data on upper and lower dentition of Metachriacus 

provocator 



Variate 


N 


R 


M 


S(d2) 


cr 


V 


LP4 


3 
3 

7 
7 
7 
7 
4 
5 
2 
2 
5 
5 
7 
7 
4 
4 


4. 8-5. 1 

2. 9 

5. 2-5. 8 

3. 9-4. 6 

5. 6-6. 

4. 6-5. 2 

6. 5-7. 
4. 0-4. 3 
4. 6-5. 

4. 8 

5. 0-5. 4 

6. 1-6. 7 
5. 4-6. 1 

7. 4-7. 9 

4. 3-4. 8 

5. 8-6. 4 


4.97 
2. 90 
5. 37 ±0.08 

4. 21 ±0.09 

5. 79±0. 05 
4. 91 ±0.07 
6.70 

4. 12 
4.80 
4.80 

5. 18 
6.30 

5. 67 ±0.09 
7. 57 ±0.07 
4.55 

6. 15 


0. 0467 


'o.'iioo' 

0. 0680 
0. 0800 


0. 1080 
0. 2600 

'6." 1700" 

0. 2700 


0. 205 ±0.055 
0.24 ±0.06 
0. 12 ±0.03 
0. 19 ±0.05 

0.24 ±0.06 
0. 18 ±0.05 




WP4 -- 




LMi 


3. 8±1. 


WMi 

LMj 


5. 7±1. 5 
2. 2±0. 6 


WM, 

LM3 


3. 8±1. 


WM3- 

LP^__ 




WP». 




LMi 




WMi 

LM2 


4. 2±1. 1 


WM2.. 

LM3.._ 


2. 4±0. 6 


WM3.. 





In only one case does the coefficient of variation exceed 5 (this 
would be true also if this coefficient were calculated for all the variates) . 



202 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 




riQUEE 50.—MetacliTiacus provocator Simpson, U.S.N.M. no. 9278, left lower jaw: a, Grown view; 6, internal 

view. Twice natural size. 




FiQUEK 51.— Metachriacus provocator Simpson: a, U.S.N.M. no. 15126, left M2-3, crown view; 6, U.S.N.M. 
no. 9259, right lower dentition, crown view. Twice natural size. 




Figure 62.— Metachriacus provocator Simpson, U.S.N.M. no. 9259, left M»-', crown view. Four times 

natural size. 



The difference from M. punitor is so obvious that its significance 
requires no proof. In every case the deviation between the means is 
significant, and in the available samples the observed ranges overlap, 
barely, only for the widths of P4 and Mi. 



FORT UNIOX OF CRAZY MOUNTAUST FIELD, MONT. 203 

The individual dimensions of the type lower jaw are as follows: 
Length P4, 5.0; width P4, 2.9; length Mi, 5.5; width Mi, 4.1; length 
M2, 5.7; width M2, 5.2; length M3, 6.5; width Mg, 4.0. 

Genus SPANOXYODON Simpson 

Spanoxyodon Simpson, 1935d, p. 236. 

Type. — Spanoxyodon latrunculus Simpson. 

Distribution. — Middle Paleocene, Fort Union, Montana. 

Diagnosis. — Pi_2 absent and long diastema between canine and P3. 
P3_4 much as in Chriacus, but P4 with metaconid larger, higher, and 
more distiuct. Mi_2 about as in Chriacus or with trigonids slightly 
lower and paraconids slightly less internal. 

Remarks. — Only one specimen referable to this genus is yet known, 
and its characters are adequately summed up in the diagnosis. 

SPANOXYODON LATRUNCULUS Simpson 

Figure 53 
Spanoxyodon latrunculus Simpson, 1935d, p. 236. 

Type. — U.S.N.M. no. 9287, left lower jaw with canine alveolus and 
P3-M2. Collected by Dr. J. W. Gidley. 

Horizon and locality. — Gidley Quarry, Fort Union, Middle Paleocene 
horizon. Crazy Mountain Field, Mont. 

Diagnosis. — Sole loiown species of genus. Measurements of type 
as follows: Length P3, 3.8; width P3, 2.3; length P4, 5.0; width P4, 2.8; 
length Ml, 5.2; width Mi, 3.9; length Mg, 5.8; width M2, 4.5. 

MIMOTRICENTES.sfl new genus 

Type. — Tricentes latidens Gidley. 

Distribution. — Middle Paleocene, Fort Union, Montana. 

Diagnosis. — Adaptively and structurally closely similar to Tri- 
centes, but Pi present, no marked diastema, and molar paraconids 
higher on crown and internal, not median, in position. 

Discussion. — In my preliminary paper I left the type of this genus 
in Tricentes, where Dr. Gidley had placed it. On further study, how- 
ever, I am forced to erect a new genus for it. The resemblance to 
Tricentes is close, but in the latter Pi is apparently invariably absent 
(the name Tricentes refers to the presence of only three premolars, 
striking in this primitive fauna), and the paraconids of M2-3 are quite 
different. The former might be only a primitive character and not 
surely of generic rank if unaccompanied by other differences. The 
character of the paraconid, however, as reduced as in Tricentes but 
in a different way, removes this form from the Tricentes lineage and 
may even mean that the relationship is not closer to that genus than 

•1 MiMoti an imitator+ Tricentes. 



204 



BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



to other primitive arctocyonids and that the resemblance is purely 
convergent, aside from the fact that both have the stereotyped pattern 
of all these ancient forms. 

The canine, preserved in the type, has a large root and is curved in 
a pronounced arc. The crown is unusually erect, as it is also in Tri- 
centes. Pi is known only by its alveolus, which is single and rather 
large. The premolars very closely resemble those of Tricentes, except 




Figure 53. — Spanoxyodon latrunculus Simpson, U.S.N.M. no. 9287, left lower jaw: a, Crown view; 6, inter- 
nal view. Twice natural size. 




Figure bi.—Mimotricentes latidens (Qidley), U.S.N.M. no. 9269, left lower jaw: a, Crown view; 6, Internal 

view. Twice natural size. 



that the heel of P4 is more expanded transversely and its posterior 
border is more nearly a straight transverse line — a distmction prob- 
ably not generic, as it is closely similar to that between Metachriacus 
punitor and M. provocator. The molars are even flatter and broader 
than in Tricentes but otherwise closely resemble those of that genus 
except for the difference in the paraconids. Upper teeth are known 
only in one specimen, mentioned below. 



FORT U^STION OF CRAZY MOUNTAIN FIELD, MONT. 



205 



MIMOTRICENTES LATIDENS (Gidley) 



Figure 54 



Tricentes latidens Gidley, Simpson, 1935d, p. 236. 

T]jpe. — U.S.N.M. no. 9269, left lower jaw with canine and P2-M3. 
Collected by Dr. J. W. Gidley. 

Horizon and locality. — Gidley Quarry, Fort Union, Middle Paleocene 
horizon, Crazj^ Mountain Field, Mont. 

Diagnosis. — Length: width ratio (type only): M2 1.09, M3 1.30. 
Measui'ements given in table 44. Paraconids vestigial and trigonids 
short. 

Discussion. — This species is Imown principally from two good 
specimens from the Gidley Quarry, the type and U.S.N.M. no. 9276, 
a right lower jaw with P2-M2 (M2 broken), confirming but not adding 
to knowledge derived from the type. There are two other specimens 
from the Gidley Quarry, probably of this species but of no value, and 
two, also very fragmentary, from the Silberling Quarry. One of the 
latter, U.S.N.M. no. 9672, with P4 and Mj, is smaller and less robust 
than the type, with the paraconid of Mi more distinct, but it might be 
a variant of this species. 

The only known upper teeth of this genus, and probably but not 
surely this species, are M^"^ from Loc. 81, in the American Museum 
collection. Like the lower molars, they closely resemble those of 
Tricentes, the only clear difference, and this of doubtful value, being 
that the internal cingulum does not circle the protocone and that on 
M^ the external cingulum does not cross the paracone. 

Table 44. — Measurements {in mm) of the two principal Gidley Quarry specimens of 

Mimotricentes latidens 





P2 


Ps 


P4 


Ml 


Mj 


M3 




L 


W 


L 


W 


L 


w 


L 


W 


L 


W 


L 


W 


9269 


3.6 
3.8 


2.8 
2.8 


4.6 
4.5 


3.3 


5.4 


4.0 
3.8 


5.5 
5.7 


4.7 
4.7 


6.0 


5.5 


6.1 


4.7 


9276 


3. 3 5. 3 

















MIMOTRICENTES ANGUSTIDENS," new species 



FlGUBE 55 

T?/2?e.— U.S.N.M. no. 9277, left lower jaw with P4-M2. Collected 
by A. C. Silberling. 

Horizon and locality. — Type from Silberling Quarry. Referred speci- 
mens, not identified with complete certainty, from Locs. 51 and 73. 
Fort Union, Middle Paleocene horizon, Crazy Mountain Field, 
Mont. 



»" Angustus, narrow+rfens, tooth. 



206 



BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



Diagnosis.— Yer J slightly smaller than M. latidens. P4 relatively 
smaller, slender, and with paraconid much stronger. Molars rela- 
tively narrower. Length: width ratio of M2 (of type) 1.24. Para- 
conids less reduced and trigonids less compressed than in M. latidens, 
trigonids about equal to talonids in size. 

Discussion. — The difference in size is slight and may not be sig- 
nificant, but the differences in structure and proportions are marked 
and sharply distinguish this from M. latidens. The type has another 
distinction, not cited in the diagnosis, in the fact that the talonid of 
M2 is definitely narrower than the trigonid, while in M. latidens it is 

of equal width or slightly wider than the 
trigonid. There are, however, two isolated 
M2's from Loc. 50 that closely resemble M. 
angustidens but that have the talonid in 
one equal to the trigonid and in the other 
slightly wider. At present it seems more 
probable that this is a variable character 
in the species than that these teeth rep- 
resent a third species. 

Princeton no. 13758 is a left lower jaw 
with M2-3, from Loc. 73, especially inter- 
esting because it is from the Fort Union 
No. 1, where fossils are very rare and be- 
cause it is, as far as I know, the only fossil 
mammal ever found in sandstone in this 
field. Its M2 agrees very closely with the 
type of M. angustidens except that the talonid is as wide as the trigo- 
nid. M3 differs from that of M. latidens in the same way as does M2, 
being relatively narrower, with stronger paraconid and longer 
trigonid. 

The dimensions of the four specimens mentioned are given in 
table 45. 




Figure 55. — MimoMcentes angusti- 
dens, new genus and species, Prince- 
ton Univ. no. 13758, left lower jaw, a, 
Crown view; 6, internal view. Twice 
natural size. 



Table 45. — Individual measurements {in mm) of lower dentition of Mimotricentes 

augustidens 



Specimen 


P4 


Ml 


Ma 


Ml 


L 


W 


L 


W 


L 


W 


L 


W 


U.S.N.M. no. 9277 


4.4 


3.0 


4.8 


3.6 


5.6 
5.6 
5.6 
5.7 


4.5 
4.6 
4.5 
4.6 


5.5 




U.S.N.M. no. 9706 




U.S.N.M. no. 9695 












Princeton no. 13758 










3.8 















rORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 207 

7MIMOTRICENTES species 

U.S.N.M. no. 6178 is a left Mj from Loc. 9, at a low level in the 
formation. It apparently belongs in this or a closely allied genus. 
Its dimensions, 6.2 by 5.2 mm, are perhaps not significantly different 
from those of M. latidens, although it is relatively somewhat narrower. 
The trigonid is distinctly longer than in the type of the genus and 
about equal to the talonid in size, not distinctly smaller as in the type. 
Although inadequate for identification, the occurrence merits mention 
in view of the horizon represented. 

Family MIACIDAE Cope, 1880 

The known history of the Miacidae is anomalous and emphasizes 
the inadequacy of some of our knowledge of details in this early epoch 
and the probably erroneous character of some negative conclusions 
regarding it. The miacids (so carefully and fully defined by Matthew 
in many works that diagnosis here is unnecessary) are a specialized 
group, for in them the carnassial shearing teeth are very well devel- 
oped, despite their absence in all other known Lower and Middle 
Paleocene mammals. Furthermore, they are an adaptive and potent 
group, for their carnassials are Mi and ?•*, as in the Carnivora (vera) 
or Fissipedia and there is every reason to believe that they are, in a 
broad sense, ancestral to all the latter. The appearance of this ap- 
parently modernized group in a fauna otherwise almost wholly archaic 
is extraordinary. 

The known distribution within the famil7 is also noteworthy. The 
first genera to appear, and the only ones known before the true Eocene, 
are not the most primitive and generalized and are not ancestral, 
even structurally, to the majority of later types. All have lost M^a, 
unquestionably present in the ancestry. Even aside from the fact 
that these teeth are present in most later miacids, they are almost 
universall}?" present in Middle Paleocene mammals of other famihes. 

This anomalous history must involve, first, rapid progressive evolu- 
tion of the group generally, the Miacidae, which is not surprising in 
view of later history, wliich shows this general type to be probably 
the most plastic and adaptive of all mammals. Second, it must involve 
the early, minor differentiation of a special fine, the Viverravinae, 
which entered the regions known to us paleontologically at about the 
beginning of the Middle Paleocene, while the more varied adaptive 
Miacinae were confined, until the great Eocene invasion, to some 
facies or region still unknown to us. 

In speaking of the Miacidae as specialized, it is important to em- 
phasize the relative value of the words. They are specialized in com- 
parison with the extraordinarily archaic contemporaneous Arctocyo- 
nidae, which are not far from being generalized primitive placentals, 
but in comparison with the other carnivores, specifically with the 



20S BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

fissipedes, they are extremely primitive, much more so than any 
Tertiary dogs or other true fissipedes. The anomaly is thus not so 
striking as might appear at first sight. Furthermore, within the family 
the Paleocene forms are distinctly more primitive than Eocene Viver- 
ravinae and are certainly not ancestral to the Aliacinae, so that com- 
parison with the latter is misleading. On a small scale, within the 
family, the Viverravinae are a miniature "archaic" radiation of 
Miacidae and the Miacinae a later "progressive" radiation, much as, 
on a far grander scale, the peculiarly specialized periptychids are an 
archaic radiation and the basically more primitive hyracotheres are 
a progressive radiation among the ungulate cohort. 

There are two distinctive genera of miacids in this fauna, Didymictis, 
evidently an abundant form with several species and long known 
from the distant Torrejon (as well as from numerous later horizons), 
and Ididopappus, a rarer type known from only two specimens in this 
fauna and as yet unknown elsewhere. 

Subfamily ViVERRAViNAE Matthew, 1909 (Viverravidae Wortman 

and Matthew, 1899) 

Viverravus, Didymictis, and Ididopappus evidently form a closely 
related group characterized, among other features, by the prominent 
anteroexternal cuspule of P*, the elongate oval outline of M^, and the 
absence of M^3 (Matthev/, 1915). For tliis group the name Viverra- 
vinae is available, contrasting with the typical miacids, the Miacinae. 
As mentioned below, Didymictis may be a compound genus, but if so 
its components are very closely related. Viverravus, also, is a some- 
what doubtfully bounded genus. Its earlier, lower Eocene species 
are very close to Didymictis, while some of its later, middle Eocene 
species, perhaps including the genotype, are so markedly advanced 
over the early forms that they might not ordinarily be placed in the 
same genus. Tliis point is not here apropos, but Viverravus is of some 
present interest because of the possibiUty of special relationship to 
Ictidopajjpus. 

Viverravus and Didymictis were separated by Matthew (1915) on 
the basis of the crested heels of Mi_2 in the former, basined in the 
latter. In fact the early species of Viverravus (e. g., V. acutus, V. 
politus, and even the slightly later V. dawkinsianus) do have basined 
talonids, although they are obviously becoming crested by emphasis 
of the hypoconid and marked reduction of the entoconid. In Icti- 
dopappus the talonids are quite as basined as in Didymictis, a condition 
doubtless ancestral for Viverravus also but partly or completely lost 
in species definitely referable to that genus. Aside from the difference 
in the heel, relatively slight at the beginning of the Eocene, the early 
species of Viverravus also differ from Didymictis in the longer, lower 
trigonid of Mi, which is a strildng resemblance to Ictidopappus. 



rORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



209 



Were it not for the unusual proportions and simple structure of P4, 
Ididopappus would make an ideal ancestor for Viverravus. Some 
species of the latter, e. g.,V. acutus, have P4 small and simple, but much 
more trenchant than in Ididopappus, stronglj^ compressed laterally, 
the posterior cusps well developed, and all cusps in a straight line, not 
subtriangular. The Ididopappus P4 might be ancestral to this, but 
there is no good evidence that it was, and Viverravus may after all be 
an offshoot of Didymidis in which the trenchant P4 was already highly 
developed in the Middle Paleocene. 

Genus DIDYMICTIS Cope, 1875 

This exceptionally long-lived genus is recorded from all levels from 
the Torrejon to the end of the lower Eocene. During this period 
there is not only definite evolutionary advance but also evidence of 
the presence of several difi'erent phyla. It is quite possible that one 
or more of these can be and should be separated generically, but the 
criteria for doing so are poor at present. A useful step was Matthew's 
(especially 1915) revalidation of Viverravus, which was long confused 
with Didymidis or considered a synonym. Now Matthew (Pale. 
Mem.) has further separated the sole Torrejon species, D. hay- 
denianus, and placed it in a new subgenus, Didymidis (Protidis), with 
the suggestion that this may prove to be of generic rank. 

The most abundant species in the present collection, D. microlestes, 
introduces some dijEculty in this arrangement. In its more important 
morphological characters it compares with the types of Didymidis 
{Protidis) and of Didymidis (Didymidis) as shown in table 46. 



Table 46.— 


-Comparison of dentition characters of three 


species of Didymictis 


Species 


pj 


Protoconeof Ml 


Proportions of M'-' 


D. (Protidis) hay- 


With rudimentary proto- 


High, angulate, posterior 


Strongly transverse, M> 


denianus. 


eone. 


wing weak. 


reduced. 






As in D. protenus 


As in B. protenus. 


D. {Didymidis) 


Compressed, no proto- 


Broader, wings equal 


Less transverse, M' less re- 


protenus. 


cone. 




duced. 


Species 


P3 


Fi 


M, 


D. (Protidis) hay- 


With very minute anter- 


With distinct, nonshearing 


With trigonid somewhat 


denianus. 


ior cuspule, heel crested 


anterior cusp, 2 talonid 


elevated and shearing. 




without distinct cusp. 


cuspules, small basin. 


heel reduced. 


D. microlestes 


With relatively large an- 


With anterior cuspule large 


Trigonid comparable to D. 




terior cusp, heel with 


and shearing, 1 talonid 


haydenianus, heel less re- 




small basin and crest 


cuspule, small basin. 


duced. 




with rudimentary cusp. 






D. (Didymidis) 


With minute anterior and 


With anterior cuspule very 


With trigonid low, tuber- 


protenus. 


large posterior accessory 


small, nonshearing, 1 ta« 


cular, heel not reduced. 




cusp, no basin. 


lonid cuspule, basin very 
poorly developed or ab- 
sent. 





210 



BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



The upper teeth, although much smaller and lighter in construction, 
resemble D. protenus rather than D. haydenianus. These are probably 
primitive characters, and D. haydenianus is slightly aberrant. The 
development of P3_4 is also somewhat closer to D. protenus, and it is 
not clear that this is wholly in primitive characters. The presence 
of only one talonid cusp on P4 may be, but it is unlikely that the more 
cuspidate P3 is primitive. The development of relatively large and 
shearing anterior cuspules on these teeth is different from either 
D. haydenianus or D. protenus and seems to be a specialization. 
M2 is perhaps merely primitive v/ith respect to either of the other 
two species. 

It is possible that D. microlestes stands nearer the D. protenus 
ancestry than does D. haydenianus, in which case the subgeneric 
separation might well be maintained, and D. microlestes would belong 
to the typical subgenus. The evidence for this is not very good, 
however, and for the present it seems best not to attempt a subdivision 
of the genus. 

There is another Didymidis-like species in the fauna, D. tenuis, of 
very diminutive size. At present it is known from a single specimen, 
and, as noted below, there is some doubt as to the chare ters of P4. 
If they were confirmed the species could hardly be placed in Didy- 
midis, but knowledge is now so imperfect that it seems best to leave 
it here until further evidence is at hand. Table 47 gives an idea of 
the very considerable differences in the length of Mi among the three 
Middle Paleocene species referred to Didymidis: 

Table 47. — Length 0/ Mi in three species of Didymictis 



Species 


N 


R 


M 


D. haydenianus- 

D. microlestes 

D. tenuis 


-Torrejon 


6 
8 
1 


7. 5-8. 
4. 3-5. 1 


7.72 
4.66 
2.9 









There are also a few specimens too imperfect for exact identification 
that are comparable in size to D. haydenianus and cannot at present 
be distinguished from that species. 

DIDYMICTIS MICROLESTES Simpson 

Figures 56, 57 

Didymictis microlestes Simpson, 1935d, p. 238. 

Type.— U.S. l^M. no. 9301, left lower jaw with P4-M2. Collected 
by Dr. J. W. Gidley. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



211 



Horizon and locality. — Gidley Quarry (one referred specimen from 
Silberling Quarry), Fort Union, IVIiddle Paleocene horizon, Crazy 
Mountain Field, Mont. 

Diagnosis. — Mucli smaller than D. haydenianus or any known later 
species (see measurements below). P3 similar to P4, but cuspules 
less well developed. P4 with large anterior cuspule, developed into 
a small shearing blade, talonid relatively broad and less rounded than 
in^other species, with one main cusp. M2 with shghtly elevated and 
shearing trigonid, talonid reduced. 




Figure 5Q.—Did'jmictis microlestes Simpson, U.S.N.M. no. 9301, with parts in outline supplied from 
U.S.N.M. nos. 6146 and 9306, left lower jaw: o, Crown view; 6, internal view. Three times natural size. 




FiGUEK 57.— Didymictis microlestes Simpson, U.S.N.M. no. 0299, with part in outline supplied from no. 
6147, left P*-M', crown view. As preserved, P» is reversed (or rotated 180°) from the position shown 
in the drawing, but this is believed to be accidental. Three times natural size. 



Discussion. — The morphological characters of this elegant little 
species have been fully brought out in the comparison and diagnosis 
above. The principal available numerical data on the lower dentition 
are given in table 48. 



Table 


48. — Numerical data on lower dentition of Didymictis microlestes 


Variate 


N 


R 


M 


a 


V 


LP4 


7 
7 
8 
8 
4 
4 


4 1-5. 
2. 0-2. 5 
4. 3-5. 1 

2. &-3. 2 

3. 4-3. 8 
2. 2-2. 3 


4. 49±0. 11 

2. 17 ±0.06 
4. 66 ±0.09 

3. 08 ±0.03 
3.65 

2.25 


0. 28 ±0.07 
0. 17 ±0.04 
0. 26 ±0.06 
0.097 ±0.024 
[2(012) =0.0900] 
[S(d2) =0.0100] 


6. 2±1. 7 


WP4 


7. 7±2. 


LM, 


5. 6±1. 4 


WM, 

LM, 


3. 1±0. 8 


WM, 





212 BULLETIN 3 69, "UNITED STATES NATIONAL MUSEUM 

The type happens to be an unusually small specimen. It measures: 
Length P4, 4.2; width P4, 2.1; length Mi, 4.3; width Mi, 3.2; length M2, 
3.4; width M2, 2.2. 

Only two upper jaws and an isolated camassial are at hand, measure- 
ments of which are given in table 49. 

Table 49. — Individual measurements {in mm) of upper dentition of Didymictis 

microlestes 



U.S.N.M. no. 


P« 


M 1 


Ma 


L 


w 


L 


w 


L 


w 


9299 




3. 9 
3.8 

4. 1 


4.2 
4.3 


5.4 
5. 1 


2.4 
2.5 


4. 


9300 


4. 9 

5. 1 


3. 9 


6147 






TlGVRE 68.— Didymictis tenuis Simpson, U.S.N.M. no. 9297, left lower jaw: a, Crown view; 6, internal view. 
P4 is broken, and it may not be correctly placed. Six times natural size. 



DIDYMICTIS TENUIS Simpson 

Figure 58 
Didymictis tenuis Simpson, 1935d, p. 238. 

Type. — U.S.N.M. no. 9297, part of left lower jaw with Mi and 
broken 7?^. Collected by Dr. J. W. Gidley. 

Horizon and locality. — Gidley Quarry, Fort Union, Middle Paleocene 
horizon. Crazy Mountain Field, Mont. 

Diagnosis. — Much smaller than any known comparable miacid. 
Ml with very elevated trigonid, hypoconid and entoconid about 
equally high and distinct. Mi length 2.9, width 1.8. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



213 



Remarks. — As the specimen is preserved there is a small tooth 
anterior to Mi that has been cemented to the specimen without any 
clear or certain contact. Knowing the care with which Dr. Gidley 
worked, I have no doubt that this tooth was found with the specimen, 
but not knowing his exact evidence of association I am not certain 
that it is in fact P4 of this individual. It is, furthermore, somewhat 
incomplete. It appears to be a very small and simple tooth with a 
short, high, conical main cusp and a single conical posterior cusp. If 
these are its true characters, it is very much unlike P4 in any species 
certainly referred to Didymictis, but this is too uncertain to draw any 
conclusion, and the lower carnassial is sufficiently Didymidis-like to 
leave the species in that genus at least until better material is found. 

DIDYMICTIS HAYDENIANUS Cope. 1882 

Figure 59 

U.S.N.M. nos. 6143 and 6145, each including an upper P*, represent 
a species inseparable from Didymictis haydenianus. Their most 
reliable dimension, the (oblique) 
length of the straight shearing edge, 
is 10.7 and 9.7 mm, respectively. 
In Torrejon specimens referable to 
D. haydenianus this dimension is 
9.2-1 1 .3 mm. No constant morpho- 
logical difference is seen. The ma- 
terial is inadequate to establish 
definitely that the Fort Union form 
is exactly the same as that from the 
Torrejon, but obviously it is not 
separable. 

In the American Museum collec- 
tion there is a specimen from Loc. 
81 with broken P* and M^ The 
oblique length of the shearing crest 

cannot be measured exactly, but it was about 11.2 mm near the 
known upper limit for D. haydenianus. The specimen is more robust 
than the two mentioned above and might be a large variant of the 
same form or a different subspecies or species. 

There is also a fragment of a P4, including the heel, U.S.N.M. no. 
9930, from Loc. 51, that has the size and cusp structure of D. hay- 
denianus, quite unlike D. microlestes. 

Genus ICTIDOPAPPUS Simpson 

Ididopappus Simpson, 1935d, p. 237. 

Type. — Ididopappus mustelinus Simpson. 

Distribution. — Middle Paleocene, Fort Union, Montana. 




Figure 59.— Didymictis haydenianus Cope, re- 
ferred specimens from the Lebo: a, U.S.N.M. 
no. 6145, left upper jaw with carnassial, crown 
view; a', same, external view; 6, U.S.N.M. no 
6143, right upper carnassial, crown view; 6' 
same, anteroexternal view; b", same, postero 
internal view in outline with wear surface cross- 
hatched. Natural size. 



214 



BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



Diagnosis. — Differing from Didymidis in the relatively smaller and 
much simpler P3-4 and relatively lower and longer trigonid of Mi, 
from Viverravus in the wider and more triangular P4 and more defi- 
nitely basined talonids, and from other known miacids in the absence 
of M3. 




Figure 



-Ididopappus mustelinus Simpson, U.S.N.M. no. 9296, right lower jaw: a, Crown view; b, in- 
ternal view. Three times natural size. 




Figure 61.— Ididopappus mustelinus Simpson, U.S.N.M. no. 9295, left upper jaw, in two fragments but 
associated, crown view. Three times natural size. 



ICTIDOPAPPUS MUSTELINUS Simpson 

Figures 60, 61 

Ididopappus mustelinus Simpson, 1935d, p. 237. 

Type. — U.S.N.M. no. 9296, right lower jaw with Ps-Mi and talonid 
M2. Collected by A. C. Silberling. 

Horizon and locality. — Gidley Quarry, Fort Union, Middle Paleo- 
cene horizon. Crazy Mountain Field, Mont. 

Diagnosis. — Sole known species of genus. Measurements below. 

Discussion. — From the alveoU the canine was a large procumbent 
tooth and was followed by a diastema. Pi may have been absent and 
Pa 1-rooted, but this is not certain. P3 is a very small and simple tooth 
consisting of a somewhat compressed main cusp followed by a shght 
unbasined heel. P4 is shorter than Mi but nearly as liigh and is sub- 



FORT UjSriON OF CRAZY MOUNTAIN FIELD, MONT. 215 

triangular. There is a small anterointernal cusp, resembling a rudi- 
mentary paraconid rather than the anterior basal cuspule of Didymidis, 
and there is a very slight and uncertain indication of a rudimentary 
basal metaconid. The talonid is very short and wide and vaguely 
cusped. There are no other cuspules or cingula. 

Ml has a large but, in comparison with Didymidis, low trigonid 
elongate anteroposteriorly. The talonid is very small, with distinct 
but not prominent hypoconid, hypoconulid, and entoconid developed 
on its raised rim. Its well-developed basin opens internally, between 
entoconid and metaconid base. M2 was evidently much reduced. 
The talonid is small but is elongate and basined, with the three cusps 
poorly differentiated. The specimen is broken immediately posterior 
to this, but from the shape of the talonid of M2 it cannot have been 
followed by another tooth. Dimensions are as follows: Length P3, 2.0; 
width P3, 1.4; length P4, 2.9; width P4, 1.9; length Mi, 3.8; width 
Ml, 2.3. 

There is a specimen, U.S.N.M. no. 9295, a left maxilla with P^, P^- 
M^, and the alveolus of the canine, that is probably the upper jaw of 
Ididopajjpus mustelinus. Its size is exactly right for occlusion with 
the type, it has P^ much smaller than in Didymidis, harmonious with 
the smaller P4 of the type, and it has M'~^ markedly shorter than in 
Didymidis, harmonious with the shorter M2 and heel of Mj of the type. 
The only feature suggesting distinction is the embrasure between 
P^ and M\ the outer angle of which is much more acute than the outer 
angle of the trigonid of Mi, which fits into it. This, however, does not 
prevent normal occlusion, as it might at first sight appear to do. In 
Didymidis, also, the embrasure angle is more acute than the occluding 
trigonid angle. Occlusion is not strictly orthal but is oblique, m part 
ectal (in fact nearly analogous to the triconodont occlusion but, unlike 
triconodonts, interlocldng). At the close of the bite the external 
trigonid angle is internal to the embrasure angle, and the trigonid fits 
mto the wider internal part of the embrasure and does not coincide 
wdth it. It cannot be proved that this upper jaw is of Ididopappus, 
but it is highly probable, and it should not be assumed to be distinct. 

The generic distinction of the upper jaw is very marked. The 
canine was relatively large, its alveolar wall swollen, much as in the 
most advanced and quite unlike the primitive species of Didymidis. 
P^ is present and a small sunple tooth probably with two roots but 
with alveolar mouths confluent. (P^ is represented by one root, the 
specimen being broken here.) P^ is much smaller than in Didymidis. 
Its ectoloph is similar in form. The pronounced inner spur, worn 
but probably not cuspidate, is median and has a separate and strongly 
divergent root. The ectoloph of P* is also similar to Didymidis but 
has a more decided notch in the external contour and is without a 
cingulum. The protocone spur is slenderer, perhaps less definitely 

119212— 3T 15 



216 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

cusped (worn) and projects almost directly internally, not at all 
forward, in marked distinction from Didymictis. 

M^~^ have the same cusp structure as in all miacids, but are highly 
peculiar in proportions, being very short and wide, markedly tri- 
angular, not at all rounded, with sharply emarginate external borders. 
These characters are more nearly approached by Viverravus than by 
Didymictis but sharply distinguish Ictidopappus from any other 
miacid. 

Measurements of this specimen are as follows: Length P^, 2.6; 
length P^ 4.8; A\ddth P*, 3.7; length M^ 3.2; width M^, 5.2; length 
M2, 2.0; width M^, 3.7. 

Family MESONYCHIDAE Cope, 1875 

This family, so widespread elsewhere in the Middle Paleocene and 
on into the Eocene, is represented in the present fauna only by two 
broken teeth. 

Genus DISSACUS Cope, 1881 

DISSACUS, species undetermined 

U.S.N.M. no. 9692 from the Gidley Quarry is the base of a tooth 
with the heel preserved. It agrees in size with Mg of Dissacus nava- 
jovius, of the Torrejon, but differs in having a very vestigial basin 
internal to the heel crest. Another specimen, from the Gidley Quarry, 
is perhaps Mi, lacking the anterior portion. The metaconid is very 
small and is relatively anterior, as in some species of Dissacus, but the 
heel is relatively shorter than in other specimens of that genus known 
to me. It is clear that these fragments are mesonychid, and there is 
nothing to distinguish them certainly from Dissacus, but they are not 
really identifiable. 

Order CONDYLARTHRA Cope, 1881 

As with most of the major groups here considered, Matthew has 
thoroughly reviewed the taxonomic history of the order Condylarthra. 
Since, however, I propose a marked change in the current arrange- 
ment of the order, an outline of tliis liistory must now be given. Cope 
proposed the name Condylarthra (then supposed to be a suborder of 
Perissodactyla) in 1881, basing it on the Phenacodontidae and princi- 
pally on Phenacodus but with Peripiychus ("Catathlaeus"), Mioclaenus, 
and Tetraclaenodon ("Protogonia") probably and Anisonchus possibly 
included. Subsequently (1882-1884) the family Periptychidae was 
distinguished, but retained in the Condylarthra, the family Menisco- 
theriidae was added, and Mioclaenus was excluded, being considered 
first an artiodactyl, then a creodont. On the latter point, Scott 
(1892) showed that many species placed in Mioclaenus by Cope were 



FOKT UNION OF CRAZY MOUNTAIN FIELD, MONT. 217 

generically distinct and were indeed creodonts, while Mioclaenvs, 
sensu stricto, might be a condylarth, in which case it would form a very 
distinct family. 

In 1895 Osborn and Earle followed Scott's suggestion and defined 
the Mioclaenidae as a family of condylarths. They retained the 
three condylarth famihes of Cope, Periptychidae, Phenacodontidae, 
and Meniscotheriidae. They divided the Periptycliidae into Anison- 
chinae and Periptychinae and stressed the resemblance of the former 
to the Mioclaenidae. They also noted that the Periptychidae had 
resemblance to the Ambtypoda and suggested the possibihty of their 
belonging there, but left them in the Condylarthra. In one of his 
last papers, in 1897, Cope adopted tliis suggestion and associated the 
Periptycliidae with the Pantolambdidae in the division Taligrada of 
the Amblypoda. In the same year, but with Cope's paper before 
him, Matthew rejected this transfer and adduced nev/ evidence and 
reasons for retaining the Condylarthra as a broad group including 
Periptychidae, Phenacodontidae, Mioclaenidae, and Meniscotheriidae. 
In 1898 Osborn adopted Cope's arrangement of the Amblypoda, in- 
cluding the Periptycliidae in the Taligrada and hence excluding it 
from the Condylarthra. °' He seems subsequently to have adhered 
constantljT- to the conception of the Condylarthra as including only 
the Phenacodontidae, Mioclaenidae, and Meniscotheriidae, and this 
authoritative view has since been the most widespread. Matthew 
continued for a time to include the Periptychidae but after about 1914 
agreed with Cope and Osborn in placing that group in the Amblypoda. 

The relationship of the hyopsodonts to this order was not estab- 
lished until relatively recently, and even now the conclusive evidence 
for it does not appear to be wddely known. From the time of its dis- 
covery by Leidy in 1870 until 1903 Hyopsodus was universally con- 
sidered to be allied to Nothardus, Pelycodus, or similar genera. It 
was therefore generall}^ considered to be a primate, occasionally an 
insectivore, but in these instances largely on the evidence of supposed 
allies, which are in fact primates. In 1903 Wortman definitely dis- 
tinguished Hyopsodus from the early lemuroids and referred it, in the 
family Hyopsodontidae (defined but incorrectly delimited by Schlos- 
ser in 1887 and recognized under an invalid name by Marsh in 1875), 
to the Insectivora, on its own characters, not those of lemuroid sup- 
posed allies. In 1909 Matthew thoroughly reviewed the Bridger 
hyopsodontids, pointed out their resemblance to the mioclaenids, and 
suggested that the two families might eventually prove to be synony- 
mous. He remarked that they lack diagnostic insectivore specializa- 
tions and expressed belief that they are closer to the Condjdarthra 
than to the more typical Insectivora. Nevertheless, he then placed 

" He inadverteDtly cites Osborn and Earle (1895) as Osborn (1892) and gives the impression that the- 
transfer of the periptychids to the Amblypoda was then proposed. 



218 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

them in the Insectivora because of their primitive character and 
because of certain marked differences from the phenacodonts. 

In 1915 Matthew reviewed the lower Eocene hyopsodonts, which, 
for the first time, gave him a good knowledge of their foot structure. 
He then considered them to be condylarths, confirming his tentative 
suggestion of 1909. He carefully redefined the Condylarthra and 
included these five famiHes, the last provisionally: Mioclaenidae, 
Hyopsodontidae, Phenacodontidae, Meniscotheriidae, and ?Pleura- 
spidotheriidae. 

In his last contribution (Pale. Mem.) Matthew retained this ar- 
rangement, except that the Mioclaenidae and Hyopsodontidae are 
reduced by further study to two subfamilies of Hyopsodontidae, as 
already tentatively foreseen in 1909. 

I now propose to return to Cope's arrangement of 1884, with the 
only change the inclusion of the Hyopsodontidae (with Mioclaeninae), 
that is, to his classical conception of a group based on both the phen- 
acodonts and the periptychids. It seems to me, after careful and 
long consideration with practically all the pertinent original specimens 
(including a good deal even unknown to Matthew), that comprehen- 
sion of this group has been retarded and taxonomy has been in a 
blind alley since the rise in the nineties of the idea of close periptychid- 
pantolambdid affinities, an idea to which even Matthew finally sub- 
scribed after som.e years of resistance. This reactionary view, which 
at this late date wiU rather seem radical, requires an outline defense 
even though much of the crucial evidence is not drawn from the pres- 
ent fauna. 

The original suggestion that Periptychus might be an amblypod 
(Osborn and Earle, 1895, p. 47) was based on the facts that its tarsus 
is not serial and that "it has the strictly trigonal molar of the Ambly- 
poda." It may at once be noted that these arguments have since 
proved to be valueless. It is now known that the primitive condy- 
larth tarsus was not serial, and the molars of Periptychidae are not, 
as a rule, strictly trigonal, those of some condylarths are, and the 
periptychid molars are otherwise decidedly more condylarth- than 
amblypod-like. 

Cope (1897, p. 335) stated that he had anticipated that the perip- 
tychids, with their astragalo-cuboid contact (nonserial tarsus), might 
be the bunodont ancestors of the Amblypoda, but he awaited dis- 
covery of their carpus and evidence that it, also, was nonserial. The 
carpus had not been discovered, but the continuing failure to discover 
any other possible amblypod ancestry led Cope then to assume the 
presence of a nonserial carpus in the periptychids and to consider 
them as this ancestry. He was also influenced by the suggestion of 
Osborn and Earle. This is too theoretical to warrant much "con- 



FORT UNIO:S' OF CRAZY MOUNTAIN FIELD, MONT. 219 

sideration. The periptychid carpus is, in fact, "alternating", but 
so is that primitive for and apparently fakly common among (other) 
condylar ths. 

Osborn (1S98, pp. 177-179, 184-186) gives a long list of taligrade 
characters as defining that group and common to pantolambdids and 
peript5xhids. The great majority of these are, as he states, primitive 
characters. As far as confirmed among the so-called Taligrada by 
later research, they are also found to occur among or to be equally 
typical of Condylarthra and hence have no bearing on the particular 
question here considered. The only progressive taligrade character 
given is ''molars triangular (tritubercular), selenodont", which is 
decidedly untrue of the Periptychidae and opposed to Osborn's thesis. 
Indeed, I cannot see that Osborn then advanced any actually valid 
evidence in favor of the conclusion given, which has since become 
taxonomic and phylogenetic dogma, largely on his authority. 

Matthew (1897) had already shown that even in the supposedly 
typical condylarths, the phenacodonts, the early forms have alter- 
nating, not serial, carpus and tarsus and that the Condylarthra there- 
fore could not be defined and were not characterized by the mooted 
primitive serial carpus and tarsus as had previously been supposed. 
He therefore found no difficulty in retaining the Periptychidae in the 
Condylarthra and gave a lucid and valid argument for doing so, even 
though, as I now think, he minimized his evidence by much over- 
stressing the resemblance of the periptychids to the pantolambdids 
in limb structure and their difference from the phenacodonts and mio- 
claenids in dental pattern. 

Upon transferring the Hyopsodontidae to the Condylarthra, Mat- 
thew (1915b, p. 311) gave a long diagnosis of the Condylarthra, in- 
volving the whole bodily structure. His intention at the time was to 
exclude the Periptychidae, since he did so in earlier and later general 
classifications, although this point was not then specifically mentioned, 
since it was foreign to the fauna he was revising. It is therefore re- 
markable and significant that his definition of the Condylarthra clearly 
excludes the Pantolambdidae but applies exactly to, and hence includes, 
the Periptychidae with a single exception: "tarsals serial." This one 
point was, in fact, an error or lapsus, for the forms he explicitly meant 
to include do not have strictly serial tarsals, and in some the approach 
to the periptychids in this respect is very close. 

Matthew's subsequent defense of the collocation of Periptychidae 
and Pantolambdidae was based almost entirely on the limbs, especially 
on the astragalus. When evidence drawn from the dentition was at 
variance with that drawn from the limbs or astragalus, he almost in- 
variably followed the latter. Without quarreling with this principle 
of research, it will appear below that the evidence is not necessarily 
at variance in the present instance. The dental evidence certainly 



220 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

favors condylarth rather than aniblypod affinities for the periptychids, 
and the Hmbs might perhaps support either view equally well and cer- 
tainly do not oppose condylarth affinities. The recognition of the 
affinities of Coriphagus, as discussed under that genus, adds to the 
evidence for the opinion supported here. 

It has been generally recognized that the teeth of the periptychids 
could not give rise to those of pantolambdids or coryphodonts. They 
are in fact aberrant and developing along a line, or series of fines, of 
their own. It has sometimes been recognized, and can readily be 
shown, that their greatest resemblance is with the Condylarthra and 
that they could all be immediately derived from types well known in 
that order. Indeed, they intergrade with certain mioclaenids to such 
a point that the families are difficult to distinguish on this basis. The 
pantolambdid-coryphodont dentitions, on the other hand, are widely 
different. Union of periptychids and pantolambdids has, then, rested 
entirely on fimb, and especially on foot structure. Indeed, without 
slighting the fact that other resemblances occur, it has depended more 
on the astragalus than on any other point. If this arrangement is a 
natural one, it seems necessarily to imply that the "taligrade" astraga- 
lus and fimb structure arose in a stock with extremely primitive teeth 
and that the widely divergent periptychid and pantolambdid denti- 
tions developed later. Such a thesis seems a priori rather improbable, 
but certainly it is not impossible. The apparently, but I think falsely, 
analogous case of the divergence of, say, suid and camelid dentitions 
after the artiodactyl foot structure arose suffices to demonstrate that 
such a history is conceivable. 

The analogy is probably false and the thesis indefensible because 
in the case of the artiodactyls the teeth, followed back in time, dis- 
tinctly converge and are rather plainly derivable from a common type 
possessed by animals that already had all the essential artiodactyl Hmb 
characters. This is not true of the periptychids and pantolambdids. 
Even within the fimits of the Periptychidae there are forms with hardly 
any suggestion of the "taligrade" foot, but wdth teeth much too dis- 
tinctly periptychid to give rise to the pantolambdids. A common 
ancestor, if it existed at all, can hardly have had taligrade feet but 
must alm.ost certainly have been a condylarth and a very primitive 
condylarth. A review (table 50) of typical astragali of the groups 
conceived will make the situation clearer. 

These genera are all of about the same age. The Hyopsodontidae 
are represented by isolated Gidley Quarry specimens surely of this 
group but not exactly determinable, as there are several hyopsodontids 
of about this size in the quarry. All five genera have numerous other 
characters of the astragalus in which they are closely similar. These 
are nondifferentiated primitive protoungulate characters, most of 
them disappearing in more advanced forms. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



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222 bulletijst 16 9, united states national museum 

All five groups are basically similar in the astragalus. The early 
Hyopsodontidae probably are most primitive in this part, and surely 
the characters that they share with Tetraclaenodon must be taken as 
primitive. From this point of view, Pantolambda is much the most 
divergent. Tetraclaenodon and the early hyopsodontids resemble 
each other very closely, almost the only differences being the greater 
elevation of the crests and excavation of the trochlea and probably 
the reduction of the cuboid contact in Tetraclaenodon Both these 
characters may be incipient speciahzations, and both are much em- 
phasized in later phenacodonts and not in later members of other 
groups. The longer, or relatively narrower, body in the hyopsodontids 
is probably of slight significance. Hemithlaeus is very close both to 
Tetraclaenodon and the hyopsodontids. Its sUghtly shorter neck, 
almost its only pecuharity with respect to the more primitive con- 
dylarths, can hardly be supposed to make this a "taligrade" astragalus, 
especially as the shortness is only relative and the neck is, in fact, 
well developed and typically constricted. The same statement applies 
to Periptychus, the neck of the astragalus being about the same in 
that genus and definitely more condylarthran than ''taligrade" in 
character. All the other characters of the astragalus are condylarth- 
ran except that the cuboid facet is about intermediate between the 
most primitive known condylarth and amblypod conditions. 

Pantolambda has a much more primitive astragalus than Coryphodon, 
yet the table clearly shows that it diverges farther from the primitive 
condylarthran condition than does Periptychus. This divergence 
consists chiefly of the appearance in rudimentary form of characters 
greatly emphasized in Coryphodon. Despite the fact that he himself 
abandoned it, Matthew's argument of 1897 in favor of considering 
Periptychus as a condylarth and Pantolambda as an "amblypod" 
seems to be as valid now as when he wrote it, indeed more so, for he 
was not then fully aware of the distinctions between these two genera 
now brought out. 

Periptychus does, of course, make some approach toward the so- 
called amblypods in Hmb structure, but this is far from reaching 
identity, and, being only vaguely or not at all seen in smaller con- 
temporaneous allies of Periptychus, may indeed be only convergent 
and largely conditioned by size and mode of locomotion. Conver- 
gence is the more likely in such forms that have not in any case come 
far from a purely primitive type of ungulate limb structure. Similarly 
Pantolambda is much more primitive than Coryphodon or other, later 
allies in limb structure, but it shows the beginning of the so-called 
amblypod type, and the approach is as much toward all or any primi- 
tive ungulates as specifically toward Periptychus and its allies. Pat- 
terson (1934) has also pointed out that the hmb structure of Bary- 
lambda tends to link Pantolambda with the coryphodonts. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 223 

The later history of the astragalus and feet in general in these 
groups is not entirely pertinent but may be mentioned. In the 
phenacodonts, culminating in Phenacodus itself, the limbs became 
considerably speciahzed in an inadaptive cursorial du-ection. Side 
toes were moderately reduced, the limbs became or remained moder- 
ately slender, and the feet digitigrade, carpus and tarsus serial. The 
astragalus differs markedly even from that of the closely allied but 
earher Tetraclaenodon. The trochlea becomes very long, the foramen 
and emargination are lost, the crests both become high and sharp, and 
the head becomes more spherical and loses contact with the cuboid. ^^ 
The hyopsodonts were remarkably conservative. As far as we know 
them, the limbs of Hyopsodus differed extremely little from those of 
its long antecedent Middle Paleocene relatives. An astragalus of 
Hyopsodus from the Eocene is almost identical with that of a Paleocene 
hyopsodontid here described except for the quite unimportant details 
of having the body somewhat less elongate and the head shghtly more 
spherical. The Anisonchinae and Periptycliinae have no known 
descendents after this stage (except for a few scraps in the early 
Upper Paleocene apparently not generically different from those of 
the Middle Paleocene). The amblypod astragalus became very 
markedly modified in Coryphodon. Its limbs are highly graviportal 
throughout, and the astragalus is profoundly modified and convergent 
toward some other graviportal types. 

The present conception of this order is as follows: ®^ 

Order Condtlarthra: 

Family Hyopsodontidae: 

Subfamily Mioclaeninae 1,t , , • - .i • ■^■ 

„ , , .,' TT 1 X- I Members of a persistently very primitive 

Subfamily Hyopsodontinae J 

group. Small, possibly insectivorous (in habits, not affinities) ani- 
mals with simple, low-crowned, bunodont teeth and clawlike unguals. 
This longest-lived group is also in almost all respects the least 
specialized. Lower Paleocene to upper Eocene. North America. 
Family Phenacodontidae: A progressively more cursorial and probably 
more strictly herbivorovis group, generally analogous within this much 
more primitive and nonadaptive radiation to the early progressive ungu- 
lates (especially perissodactyls) that replace them in the Eocene. Teeth 
brachyodont, becoming polybunous with some slight tendency toward 
lophiodonty. Lateral toes becoming somewhat reduced and unguals 
flattened into hoofs. Middle Paleocene to lower Eocene. North America, 
South America, Europe. 



" Some of these characters were supposed to be typical of the Condylarthta, because Phenacodus was 
ihe only adequately known genus when the order (or suborder, then) was first defined, and it may seem 
strange to consider Phenacodus as a peculiar and in many respects atypical condylarth. It is, in some 
sense of the word, technically a "type" of the Condylart.hra, but it is definitely n(n typical throughout. 
Taxonomy has many such cases in which a natural group was recognized and named, even though in the 
first instance it was largely based on a form later found to be marginal in it. 

»3 Matthew has given excellent diagnoses of all the groups concerned. These characteristizations are 
meant to be explanatory, not formally diagnostic. 



224 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

Order Condylarthra — Continued. 

Family Periptychidae: Cliaracterized by persistently plantigrade feet and by 
teeth markedly bunodont, the premolars not becoming molariform (as in 
other families) but evolving independently into large swollen crushing 
teeth, the molars relatively small, with the primary cusps conical and 
crowded together, developing a peculiar type of polybuny especially 
in the upper teeth by the development of new cuspules largely internal to 
the primary cusps. 

Subfamily Anisonchinae: Small and slender forms with the basic dental 
characters of this family, but the teeth relatively simple and general 
structure apparently closely similar to the Hyopsodontidae. Lower 
to Middle Paleocene. North America. 
Subfamily Periptychinae: Larger subgraviportal forms developing heavy 
limbs and somewhat amblypodlike feet, with complex, polybunous 
molars. Lower to Upper Paleocene. North America. 
Family Meniscotheriidae: Hyracoidlike animals of middle size with lopho- 
or buno-selenodont teeth, serial carpus and tarsus, and narrow, hooflike 
unguals. Their early history is unknown and their relationships doubtful. 
They may not be very close to the other condylarths. Their dental evolu- 
tion seems to have been in a direction distinct from any other primitive 
ungulates, and almost opposite that of the periptychids, but could have 
started from a common basis in the Paleocene. 

Subfamily Meniscotheriinae: Typical, more lophiodont forms. Upper- 
most Paleocene and lower Eocene. North America. 
Subfamily Pleuraspidotheriinae: More bunodont forms, of still more 
dubious position. Upper Paleocene. Europe. 

In the present fauna the Hyopsodontidae are very abundant and 
varied. Phenacodonts are present but are not abundant, being espe- 
cially rare in the quarry facies. Anisonchines are not uncommon 
but are limited in variety, only two genera and species being recog- 
nized, and are much less common or varied than in the Puerco and 
Torrejon. The Periptychinae, so common in the San Juan Basin 
faunas, appear to be wholly lacking. Meniscotheres are absent, as 
would be expected since this group is Imown only from younger strata. 

Family HYOPSODONTIDAE Lydekker, 1889 

The small Paleocene animals now believed to be condylarths allied 
to Hyopsodus have had a confusing and complex history, which is 
here to be sketched only in its more essential points. Cope's genus 
Mioclaenus was at first referred by him to the Condylarthra, but he 
later removed it to the Creodonta on the basis of the skeletal characters 
of "Mioclaenus" ferox. Pie referred many species to the genus, mak- 
ing it a sort of dumping ground for unspecialized dentitions of more 
or less bunodont, tubercular-sectorial type. Schlosser, in 1886, sug- 
gested that Mioclaenus might really be a condylarth (as Cope origi- 
nally supposed). Scott (1892) separated out a number of Cope's 
species and placed them in distinct genera. "M." ferox was then 
made the basis for the genus Claenodon, a true creodont. Scott then 
considered that true Mioclaenus, really allied to the type M. turgidus, 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 225 

might be a condylarth genus, in which case "it will form a very 
distinct family of that order." 

Osborn and Earle (1895) placed Mioclaenus in the Condylarthra 
and proposed a new family Mioclaenidae. They discussed only 
M. turgidus and evidently intended to include in the family only 
Mioclaenus and in that genus only the few species not definitely 
removed by Scott. Matthew (1897) hesitated in regarding the Mio- 
claenidae as condylarths but did leave them in that group. He placed 
in the genus Mioclaenus the species Tricenies inaequidens Cope, which 
Scott (1892) had made type of the genus Ellipsodon, and he proposed 
a new genus Protoselene for Mioclaenus opisthacus Cope. 

In their 1895 paper, Osborn and Earle described a new genus 
Oxyacodon, listed as incertae sedis but in the vicinity of the creodonts. 
Matthew (1897) left the genus as incertae sedis and transferred to it 
Anisonchus agapefillus Cope. In 1914, in a faunal list, Alatthew 
transferred Oxyacodon to the Mioclaenidae, with a footnote that it 
might be a periptj^chid. In his subsequent work (see Pale. Mem.) 
Matthew confirmed the association of Oxyacodon with Mioclaenus 
and transferred to it the other Puerco species, ^^Mioclaenus" turgi- 
dunculus, thus confining the genus Mioclaenus {sensu stricto) to the 
Middle Paleocene. He also revived Ellipsodon Scott and placed in 
it Mioclaenus acolytus Cope and Mioclaenus lemuroides Matthew. 

The arrangement reached b}^ Matthew is thus as follows: 

p „ , jType: 0. apiculatus. 

[Referred: 0. agapetillus, O. tiirgiduncvhis, 0. ■priscilla. 
,,. , [Type: M. turgidus. 



Torre j on ' 



p,,, . , jType:S. inaequidens. 

[Referred: E. lemuroides, E. acolytus. 
Protoselene: Type: P. opisthacus. 



The history of the Eocene group Hyopsodontidae has been suffi- 
ciently noticed in connection with the discussion of the Condylarthra 
as whole. Matthew early recognized that the hyopsodontids and 
mioclaenids were related and in 1909 suggested that future discovery 
might result in merging the two supposed families. In his Paleocene 
memoir he toolc this step, retaining the earlier double grouping in the 
form of two subfamilies, Hyopsodontinae with Haplomylus and 
Hyopsodus and Mioclaeninae with the earlier genera listed above. 

After Matthew's work numerous discoveries of new hyopsodontids 
have been made. Jepsen (1930) described Litolesies and Phena- 
codaptes from the Upper Paleocene of Wyoming. He placed the 
former doubtfullj'" in the Insectivora and the latter doubtfully in the 
Artiodactyla, but I have already suggested (Simpson, 1936b) that 
they are probably hyopsodontids. Finally there are three new 



226 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

genera of hyopsodontids in the present fauna, Haplaletes, Litomylus, 
and Litalestes. The number of known genera has nearly doubled 
since Matthew completed his work, and the whole unwdeldy group 
requires reconsideration. The genera now known and considered 
hyopsodontid are as follows: 

Choeroclaenus (defined below): Type C. turgiduncnlus. Lower Paleocene. 

Oxyacodon: Tj^pe 0. apiculatus. Lower Paleocene. 

Mioclaenus: Type M. turgidus. Middle Paleocene. 

Elli-psodon: Type E. inaequidens. Middle Paleocene. 

Protoselene: Type P. opisthacus. Middle Paleocene. 

Litaletes: Type L. disjunctus. Middle Paleocene. 

Litomylus: Type L. dissentaneus. Middle Paleocene. 

Haplaletes: Type H. disceptatrix. Middle Paleocene. 

Litolestes: Type L. ignotus. Upper Paleocene. 

Phenacodaptes: Type P. sabulosus. Upper Paleocene. 

Haplomylus: Type //. speirianus. Uppermost Paleocene and Lower Eocene. 

Hyopsodus: Type H. paulus. Lower to Upper Eocene. 

The types and many other specimens of these genera have been 
eexamined for the present work ^* in order fully to analyze the affini- 
ties of the Fort Union forms here described and their contribution 
to knowledge of the family. 

In the first instance, generic designations were disregarded and the 
18 well-defined Paleocene species referable to this family were graphi- 
cally compared by a tabulation of all their known characters. ^^ 
They were found to fall naturally into groups that correspond very 
well with the various genera recognized by Matthew and those 
defined after his work. The principal characters distinguishing 
these generic groups are shown in the following key, which also gives 
(in parentheses) the species now placed in each genus, the type being 
indicated by an asterisk. 

KEY TO THE PRINCIPAL GENERA OF HYOPSODONTIDAE KNOWN IN THE PALEOCENE 

I. Paraconids internal, fusing with metaconids; entoconids indis- 
tinct, fusing with hypoconulids. 
A. P^ enlarged, inflated, few accessory cuspules. 

1. Paraconids less internal, entoconid distinct on M2, few or no 

crenulations, M3 large, with projecting hypoconulid, M* 

with large metacone Choeroclaenus ^^ (turgidunculus*) 

2. Paraconids wholly internal, entoconid indistinguishable on 

M2, crests crenulated. M3 much reduced, with rounded 

heel. Metacone vestigial on M^ Mioclaenus (turgidus*) 



" Material of Litolestes and Phenacodaptes through the courtesy of Dr. Q. L. Jepsen. The American 
Museum collections includemostof the types and many excellent specimensof all the genera except PAcnaco- 
daptes. The type specimen of Hyopsodus paulus was not seen, but many good specimens of this and other 
species of Hyopsodus were examined. 

'3 Two or three poorly known supposed species of doubtful status were omitted. 

'8 New genus, defined on p. 232. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 227 

B. F*4 cuspidate, more or less enlarged but not inflated. 

3. P4 without distinct paraconid, metaconid absent or rudi- 

mentary, talonid relatively wider, M^3 much to somewhat 
reduced. 
Ellipsodon (inaequidens*, prisons, leniuroides, acolytus, aquilonius) 

4. P4 with rudimentary paraconid, metaconid relatively large, 

talonid narrow, M^ relatively large Litaletes (disjvinctus*) 

//. Paraconids median to subinternal, not fusing with metaconids, 
entoconlds distinct, molar talonids basined. 

C. Teeth more lophiodont, P4 bicrescentic, paraconids distinct, 

P^ with metacone, M'"- with strong mesostyle, M^3 large. 
5 Protoselene (opisthacus*) 

D. Teeth more bunodont, paraconids reduced or vestigial, no 

mesostyles, M^3 generally somewhat reduced. 

a. P4 without distinct paraconid, but relatively elongate and 

trenchant, M3 large, with projecting hypoconulid, molar 
cusps acute. 

6. P4 with rudimentary metaconid, molar paraconids rela- 

tively large Oxyacodon (apiculatus*, agapetillus, priscilla) 

7. P4 with distinct metaconid, with a pit between this and 

protoconid, molar paraconids reduced Litomylus (dissentaneus*) 

b. P4 with distinct small paraconid but relatively wide and 

heavy, M3 somewhat reduced, molars bunodont, generally 
broad and low. 

8. P4 with smaller metaconid and talonid, talonid of M3 less 

elongate, upper molars more transverse and angulate, 
outer cusps of P^"* more compressed. 

Litolestes (ignotus*, notissimus) 

9. Metaconid and talonid of P4 larger, M3 more elongate, P^~* 

with more conical outer cusps, upper molars rounded and 

less transverse Haplaletes (disceptatrix*) 

c. P4 elongate, with strong paraconid, M^3 reduced, prominent 

cingulum descending from protocone tip. 
10 Haplo mylus (speirianus*) 

Like all keys, this is artificial, but it is based oq an extensive analysis 
of the characters of all the species listed, and an effort has been made 
to select characters that have clear taxonomic value and are probable 
or possible indications of phyletic relationships. Thus it is believed 
to be probable that the capital letters indicate four natural groups of 
genera. The primary division, indicated by Roman numerals, also 
appears to me (but with somewhat less probability) to be a natural 
dichotomy of the whole group. 

Matthew has suggested that Choeroclaenus turgidunculus, which he 
referred to Oxyacodon, might be ancestral to one or more species of 
Ellipsodon. The resemblance is certainly close, and I believe a 
relationship to exist. It seems to me, however, to be that indicated 
above by group / and hence more general than he suggested and 
inclusive of Alioclaenus, sensu stricto. In more exact phyletic relation- 
ship, Choeroclaenus turgidunculus appears to be closer to Mioclaenus 
turgidus The resemblance in the molars is as close as to Ellipsodon, 



228 BULLETIN 1(3 9, UNITED STATES NATIONAL MUSEUM 

and the premolars are practically those of Miodaenus in miniature and 
unlike those of Ellipsodon. Furthermore, the rather poorly known 
Ellipsodon priscus carries that genus, or something very like it and 
probably closely related, back into the Lower Paleocene, contempo- 
raneous with Choeroclaenus . 

The group of species referred to Ellipsodon is rather heterogeneous, 
as discussed under that genus. The presence of so many varied 
species shows that several divergent minor phyla are present, but all 
appear to be rather closely allied. Ellipsodon priscus represents a 
possible an estral tj^pe of structure, without being clearly allied to 
any particular one of the Middle Paleocene species. The other species 
are all approximately contemporaneous and so represent a spreading 
out of the group without permitting the discernment of any special 
lines of descent. 

Oxyacodon represents the second major group in the Lower Paleo- 
cene. Its distinctive characters are almost entirely primitive and it 
affords a structural ancestry for its general group, D. It is improbable 
that the ancestry of Protoselene would enter into Oxyacodon, and the 
case of Haplomylus is also dubious. Upper teeth of Oxyacodon are 
unlaiown, and might considerably modify the present conception of 
the genus. 

Litomylus very closely resembles Oxyacodon but is in at least two 
respects, molarization of P4 and reduction of molar paraconids, a more 
advanced form. As far as the scanty data go, it could be a relatively 
unprogressive descendant of Oxyacodon. 

Haplaletes and Litolestes, both possible structural derivatives of 
Oxyacodon, are successive, Middle and Upper Paleocene, respectively, 
and appear to be close relatives, but they cannot be along exactly the 
same line of descent, at least in the known species. Litolestes, the 
later genus, is probably more specialized in the reduction of M^3 and 
perhaps in the more transverse upper molars, compression of P^~^, 
and some other details, but its premolars seem to be slightly but dis- 
tinctly less progressive than in Haplaletes. (Its known species are 
also somewhat smaller than Haplaletes disceptatrix.) 

Haplomylus appears at the end of the Paleoc6i_3 and runs into 
the lower Eocene. It is clearly a member of this general group, but 
none of the older genera is enough like it to suggest any very close 
structural ancestry. Its general premolar and molar structure, 
although somewhat more advanced as would be expected, is of the 
type of group D of the foregoing key and is such impelling evidence 
of relationship that the genus has been classed with that group. 
At the same time some important details are not foreshadowed in 
any of the other genera. The most striking point, the development 
of the posterointernal part of the upper molars as a broad cingulum 
sweeping down from the protocone, curiously reminiscent of some 
of the ancient primates, is approached (but not very closely) in 



FORT UNION OF CRAZY MOUNTAIIST FIELD, MONT. 229 

Ellipsodon, but the other characters of the dentition ahnost exclude 
the possibihty of special relationship. 

Protoselene is a more sharply defined genus than any of the others 
here considered. It has the general characters of a prmiitive hyopso- 
dontid but is evidently becoming specialized throughout the dentition 
in a way hardly suggested by any other genus. 

Hyopsodus is not inserted in the above key, because it is not known 
in the Paleocene and because it is so distinctive that it can be recog- 
nized at a glance, and confusion with the Paleocene genera is impos- 
sible. This distinctive character, however, is entirely in features 
demonstrably progressive, and anyone who studies the whole structure 
of Hyopsodus, particularly with reference to the evolution that 
occurred within that genus, can hardly fail to endorse Matthew's 
conclusion that it is an ally of the Paleocene forms here discussed. 
The genera discovered since Matthew's work still more strongly 
substantiate the reality of this relationship, for it may now be said 
that Hyopsodus has no known structural character not clearly 
developed or adumbrated in the Paleocene hyopsodontids." 

Hyopsodus most nearly resembles group D of the foregoing key, 
and m a general way this group has every essential requirement for 
the structural ancestry of the Eocene genus. Its most exact resem- 
blance in details appears to be with Haplaletes. The sequence 
Oxyacodon-Haplaletes -Hyopsodus is, as far as it is known, one in 
which no difficulty opposes its acceptance as a structural phylum. 
There are no "crossing speciahzations", and all characters seem to 
be modified uniformly and in one direction in accord with the relative 
ages of the genera. At the same time it is, of course, apparent that 
the data are inadequate to prove that this is an exact genetic 
phylum, and, as in most cases, the probabilities are very much against 
our having in collections the exact members of the true line of descent. 

There remams for discussion only Phenacodaptes Jepsen, 1930. 
This has not been inserted in the key because its afiinities with 
the other genera are not definitely established, and Dr. Jepsen has 
material that he has not yet described and that may give a better 
basis for decision. From his published data, the genus appears to 
me to enter into the Hyopsodontidae. It has characters strongly 
suggestive of the dichobunid artiodactyls, but so has the whole 
Paleocene group of hyopsodontids. It is, indeed, almost impossible 
to frame a diagnosis, on dental characters alone, that will surely 
distinguish hyopsodontids and artiodactyls, yet such skeletal parts as 
are known show that they were quite distinct, at least in the lower 
Eocene, and even the dentitions give a definite feeling, supported 

" Mile. Friant's recent reference of Hyopsodus to the Insectivora and strange discussion ot the derivation 
of insectivore, especially erinaceoid, molar patterns can be quite ignored. She seems to te wholly unaware 
of any of the evidence for the true affinities of Hyopsodus. 



230 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

by distinctions open to exception but fairly distinctive with tiie whole 
group in mind, that they are different groups. Whether it be con- 
sidered as a dichobunid or as a hyopsodontid, Phenacodaptes is a 
peculiar form. Yet ail its characters known to me are either dupli- 
cated or rather closely approached by various hyopsodontids, and its 
reference to that group is at least as probable as any other view. The 
fact that no artiodactyl, or no other artiodactyl, is known from the 
Paleocene in itself carries no great weight as regards the affinities of 
Phenacodaptes, except from the point of view of logical procedure in 
the special case. If, as seems to me to be true, Phenacodaptes re- 
sembles a group that is known to have been abundant and varied 
when it lived at least as closely as it resembles another that has never 
been found in deposits of that age, it seems preferable to refer it to 
the former group pending discovery of decisive evidence. 

If Phenacodaptes should prove to be a hyopsodontid, it will not 
very closely enter any of the categories of the key, not so much that 
it has any nonhyopsodontid character as that it is a synthetic type. 
The lower premolars are somewhat more suggestive of group /, 
although they could well appear also in group //. The molar tri- 
gonids, as far as I can judge by the data known to me, may be either 
Ellipsodon- or Haplaletes-like, probably the former, but the entoconids 
are more as in Haplaletes and its allies. 

Supergeneric grouping of these forms has always been based on a 
separation of Hyopsodus from all other known forms. Historically it 
is easy to see how this arose and that it was logical to the point of 
being the only arrangement permitted by the data. Hyopsodus is, 
within this group, an advanced genus with pronounced modifications, 
tending to conceal its relationships to the very primitive forms. 
Even within the genus, knowledge was principally based on relatively 
late (especially middle Eocene) and specialized species. Further- 
more the only Paleocene forms adequately known were from the 
Lower and Middle Paleocene and were typified by such a form as 
Mioclaenus turgidus, which lies rather far from the structural ancestry 
of Hyopsodus. 

Even Matthew necessarily based his conception of the genus on 
forms that suggest marked separation from Hyopsodus within the 
family. Aside from Mioclaenus he knew only Oxyacodon, Ellipsodon , 
Protoselene (with Haplomylus in latest Paleocene and early Eocene). 
Oxyacodon is so ancient and primitive that intermediate stages were 
necessary to show its probable phyletic position. Ellipsodon now 
appears to lie nearer Mioclaenus, at least in its typical species, than 
to the more Hyopsodus-like genera. Protoselene is curiously divergent 
and not very near any other genus. He regarded Haplomylus as to 
some extent intermediate between the earlier forms and Hyopsodus, 
and probably this largely influenced him in uniting the Hyopsodon- 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 231 

tidae and Mioclaenidae, but he saw that Haplomylus could not be 
ancestral to Hyopsodus and was not clearly derivative from any 
known Paleocene form, so that the evidence was inconclusive. 

The discovery, since Matthew, of several Middle and Upper Paleo- 
cene genera that are clearly related to Mioclaenus and Ellipsodon but 
that approach Hyopsodus much more closely than do those two 
genera has much altered the conception of this family. It is now seen 
that in the Paleocene there are a less Hyopsodus-\ike and a more 
Hyopsodus-like group. The distinction of the Hyopsodontinae, with 
Hyojjsodus only, depended in part on progressive characters, sure to 
become uncharacteristic when forms of intermediate age and structure 
were found, and in part on what appear to be valid phyletic characters 
which separate Hyopsodus from one group of Paleocene genera, but 
associate it with the other. On present data, it seems preferable to 
base supergeneric classification on these latter characters and to draw 
the line not between the Paleocene forms and Hyopsodus but between 
those of the Paleocene forms that are less and more like Hyopsodus, 
grouping that genus with its closer relatives among the older genera. 

Subfamihes drawn upon this basis are defined below. This arrange- 
ment is still only tentative, and it is clear from the discussion of 
generic relationships above that a great deal must yet be learned 
before a really well-founded classification witliin the family will be 
possible, but the new arrangement perhaps represents a step toward 
this end. The most doubtful points, as regards the forms now known, 
are the affinities of the more atypical species placed in Ellipsodon and 
of Litaletes, the true place in the system of the rather isolated genus 
Protoselene, that of the apparently aberrant Haplomylus, and the 
relationships of Phenacodaptes. 

The new evidence substantiates without greatly altermg the grounds 
for considering the hyopsodontids as condylarths, sufficiently set 
forth by Matthew. Discovery of intermediate forms makes the 
family more coherent than it seemed to him and improves the evidence 
for considering the relatively well known Hyopsodus as indicative of 
the affinities of the Paleocene genera, and so strengthens his conclu- 
sions. The resemblance of the early hyopsodontids to the dichobunids 
in the dentition is so remarkably close that it is difficult to ascribe it 
entirely to convergence. Although the known skeletal parts are not 
of artiodactyl type, it is quite possible that some branch of the earliest 
hyopsodontids did give rise to the Artiodactyla, but this can be proved 
or disproved only by further discovery. Even if this should prove 
to be the case, the hyopsodontids as a whole would probably be best 
classified as Condylarthra, since they had the general characters of 
that order, and retained them after the ancestral artiodactyls were 
distinctly differentiated in the skeleton. 

119212—37 16 



232 BULLETIlsr 16 9, UNITED STATES NATIONAL MUSEUM 

Subfamily MiocLAENiNAE Matthew (ex ms.) (Mioclaenidae Osborn 

and Earle, 1895) 

Bevised definition. — Paleocene hyopsodontid condylarths with P^4 
more or less enlarged and sometimes inflated. P4 generally relatively 
simple, with small talonid. Molar paraconids reduced, internal, 
fusing with metaconids. Molar talonids generally open, entoconids 
reduced, fusing with hj^poconulid and becoming vestigial. M^3 
often more or less reduced. M^~^ with very weak or no hypocone, 
posterior cingulum tending to run to tip of protocone. 

This subfamily is redefined to include Mioclaenus, its structural 
ancestor Choeroclaenus , Ellipsodon, and (doubtfully) Litaletes, and to 
exclude Protoselene, Oxyacodon, and some other genera formerly 
placed in it. Choeroclaenus does not occur in the fauna here under 
discussion, but it is defined below because reconsideration of the whole 
family demands the proposal of this new name. Ellipsodon and 
Litaletes have species in this fauna and are further considered in con- 
nection with these species. 

CHOEROCLAENUS ^s, new genus 

Type. — Mioclaenus turgidunculus Cope, 1888. 
Distribution.- — Lower Paleocene, Puerco, New Mexico. 
Diagnosis. — P'*4 bulbous, inflated. P4 without anterior cuspule, 
paraconid or metaconid, talonid very small, wdth one faintly crested 
cuspule. Molar paraconids small but distinct, nearly confluent with 
metaconids but not wholly internal. Entoconids distinct and about 
as high as hypoconulids, molar talonids basined. M^3 little or not 
reduced. M3 with projecting hypoconulid. M^~^ transverse, with 
sharp external, anterior, and posterior cingula. Hypocone indistinct, 
posterior cingulum tending to connect with protocone tip, M^ with 
well-developed metacone. Connies small, distinct. Cusps low but 
sharp and clear-cut, crenulations and proliferation of minor cuspules 
slight or absent. 

Discussion. — The type species rather closely resembles the type of 
Mioclaenus, M. turgidus, and has almost invariably been referred to 
that genus.^^ It is, however, sharply distinguished by the characters 
given above and in the key on a previous page. Most of these dis- 
tinctions are primitive characters, and they tend to link this form, 
more nearly than the later and more aberrant Mioclaenus turgidus, to 
the small and more generalized early hyopsodontids. Matthew, the 
only person who had critically examined the specimens since Cope, 
recognized this and recorded it (Pale. Mem.) by transferring the species 
to the primitive genus Oxyacodon, a structurally defensible and reason- 
's XoTpos, pig, + claenus, a combination meant to suggest the dental resemblance to bunodont artiodactyls, 
relationship to Mioclaenus, and derivation from the Puerco beds. 

'• The single exception, previous to Matthew's last work, seems to be Roger, who placed it in Protogonodon 
in his catalog, but the reason for this is not apparent. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 233 

able assignment. Our present greatly expanded knowledge of Middle 
Pal eocene hyopsodontids, however, throws emphasis on certain charac- 
ters that now appear to be more important phyletically than those 
previously apparent. The premolar inflation is unlike Oxyacodon 
both in kind and degree and points toward Mioclaenus, s. s., and not 
Ellipsodon. In the lower molars the position, shape, and connections 
of the paraconid are very much unlike Oxyacodon and point toward 
Mioclaenus and Ellipsodon rather than toward Litomylus and Hap- 
laletes (described since Matthew's death) as does Oxyacodon. The 
entoconids are, indeed, distinct, an Oxyacodon-like character, but they 
are definitely fusing with the hypoconulid and do not suggest continued 
independence as in the group to which Oxyacodon belongs. (No Middle 
Paleocene genus known to Matthew belonged to this group, although 
it is now richly represented, and so he could not evaluate the impor- 
tance of this character.) The upper teeth are not known in true 
Oxyacodon, but the characters of the lower teeth sharply distinguish 
Choeroclaenus from that genus. 

Genus ELLIPSODON Scott, 1892 

This genus is revised in Matthew's memoir. It is unusually varied 
in structure, and the species here referred to it increases this variety. 
Ellipsodon aquilonius, of this fauna, closely resembles E. acolytus. The 
latter is fairly close to E. lemuroides, which in turn approaches E. 
inaequidens. There is no logical or convenient separation, probably 
of more than specific rank, in this series of four species, yet E. aquilonius 
is markedly unlike E. inaequidens, which is the type of the genus. 
Whether any generic or subgeneric separation is proper, must depend 
on future discovery. At present it seems that the genus may be too 
broadly drawn, but this is not demonstrated inequivocably, and it 
probably is a natural genus in the sense that the species referred to it 
are related to each other. 

The type species, E. inaequidens, is poorly known. The type speci- 
men is a palate with P^-M^ of one side or both, all the teeth deeply 
worn, and the palate encased in hard concretion. Another palate is 
less worn, but even more obscured by concretion, and a third shows 
M^~^ fairly well preserved. Lov/er jaw fragments reveal P4-M3. All 
the few surely referable specimens were collected by Baldwin for Cope 
in 1882 to 1885, and the great collections made subsequently contain 
only one specimen possibly referable to the species, and this one is 
highly dubious. As far as their localities are recorded, Baldwin's 
specimens all came from Gallegos Canyon, and it is possible that they 
are from some local pocket worked out by him or not well exposed 
when later collectors visited the area. The unusual circumstance 
that the type is the poorest known species of the genus and has not 
turned up in new collections for over 50 years makes the status of the 



234 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

genus somewhat uncertain. The structure of P4, the extreme reduc- 
tion of M3, and perhaps some less clear details are peculiar with respect 
to E. lemuroides or E. acolytus, and the fact that the genus is known 
principally from these atypical species may mean that its true nature, 
as based on E. inaeguidens, is now seriously misunderstood. 

In general aspect, E. aquilonius resembles some of its associates 
such as Litaletes disjundus more than it does Ellipsodon inaeguidens, 
but in structural detail it seems closer to Ellipsodon acolytus and is 
conservatively associated mth that species generically (rather than 
definitely with the type of Ellipsodon). 

ELLIPSODON AQUILONIUS Simpson 

Figures 62, 63 
Ellipsodon aquilonius Simpson, 1935d, p. 242. 

Type. — U.S.N.M. no. 9280, right lower jaw with P3-M3 and alveoH. 
Collected by A. C. Silberling. 

Paratype. — U.S.N.M. no. 9567, right upper jaw with P^-M^. 
Collected by Dr. J. W. Gidley. 

Horizon and locality. — Types from Gidley Quarry, surely referable 
specimens from Silberling Quarry and one, more doubtful, from Loc. 
51, Fort Union, Middle Paleocene horizon, Crazy Mountain Field, 
Mont. 

Diagnosis. — Close to E. acolytus in size and structure, but teeth 
generally slightly slenderer, P4 relatively shorter and with metaconid 
more distinct. M^a only moderately reduced. P^ without protocone. 
M^~^ with rudimentary hypocone not connected to protocone apex. 
Measurements given below. 

Discussion. — This is one of the commonest species in the quarries 
and is represented by a fine series of specimens revealing its dental 
morphology and variation in detail, although in no case is the anterior 
dentition preserved. 

The number of incisors is unknown. The post-incisive dentition 
was complete numerically. 

The upper canine and P^ are unlaiown. P^ is a small simple tooth 
with a small anterior and a larger posterior root. The crown is com- 
pressed, trenchant, with a median cusp, minute posterior cuspule, and 
posterointernal cingulum. P^ has three roots but is longer than wide 
and has only one distinct cusp, which is central and is triangular in 
section, with minute anterior and posterior basal cuspules and a 
sharp, continuous, but not cuspidate internal cingulum, stronger on 
the posterointernal than on the anterointernal face. P* is wider 
than long and has a strong protocone, which is, however, lower than 
the amphicone. There is no separate metacone. The amphicone is 
triangular and has a sharp posterior and a weak anterior crest from 



FORT UNIOISr OF CRAZY MOUNTAIN FIELD, MONT. 



235 



the tip. There is a distinct parastyle and small vague metastyle. 
The entire crown is circled by a cingulum which bears a cusp, topo- 
graphically a metaconule, near the middle of the posterior border. 




Figure 62.- 



-Ellipsodon aquUonius Simpson, U.S.N.M. no. 9280, right lower jaw: a, Crown view; 6, in- 
ternal view. Two and one-half times natural size. 




Figure 63.— Ellipsodon aquUonius Simpson, U.S.N.M. no. 9567, with parts in outline supplied from 
U.S.N.M. nos. 9571 and 9576; left upper jaw: a, External view; b, crown view. Four times natural size. 



M^ and M^ have the same structure but differ in size and proportions. 
Although distinct, the paracone and metacone are crested and the 
crests tend to form a simple ectoloph. The protocone is crescentic 
and its wings bear definite protoconules and metaconules, just internal 
to paracone and metacone. There is a sharp, continuous external 
cingulum, small definite parastyle, very vague metastyle, and no 
mesostyle. The pronounced anterior cingulum stops short at the 
anterointernal corner without rising or rounding the long mternal 
slope of the protocone. The otherwise similar posterior cingulum 



236 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

rises toward the protocone apex at the inner end and terminates in a 
definite point, a rudimentary hypocone on the posterior protocone 
slope and near, but separate from, the protocone tip. M^ is oval, 
with rounded comers, and is reduced but much less so than in E. 
inaeguidens. It has a vestigial but distinct metacone. 

The lower canine is known only from its single, cyhndrical root, 
which indicates a small tooth (but larger than Pi) only slightly 
procumbent. Pi has one small root and a slightly procumbent and 
recurved simple crown, excavated on the posteromternal face. 
P2 is considerably larger, 2-rooted, and with a single distinct heel 
cusp. P3 is transitional to P4 in structure, with the heel considerably 
expanded and a curved crest and excavation at the anterointernal 
angle. P4, although sharply distinct from the molars, is more nearly 
molariform than in any other species referred to this genus. There is 
a low distinct metaconid on the posterointernal protoconid slope, at 
about two-thirds of the distance from the base to the apex of the crown. 
The anterointernal protoconid slope is excavated, and the anterior 
protoconid crest curves inward and then posteriorly around it, gener- 
all}'' without forming a cusp but in a few specimens with a very rudi- 
mentary and low paraconid. The talonid has a slight crest ending 
in a cusp at the posterior margin, somewhat external to the midline, 
with a vague, open internal basin and a small posterointernal cuspule. 

Ml has the protoconid and metaconid opposite, the metaconid 
slightly the larger of the two. The paraconid is distinct, fully 
internal, partly connate with the metaconid, and smaller and lower 
than the latter. The talonid is nearly as high as the trigonid and is 
well basined, but with the basin open in a narrow notch between 
entoconid and metaconid. The hypoconid is large, distinct and 
crescentic. The small hypoconulid and larger and equally high 
entoconid are poorly separated. When quite unworn, three small 
cuspules are seen, one on the anterior hypoconid wing, one on the 
posterior metaconid slope, and one on the anterior entoconid crest. 
The talonid is wider than the trigonid. M2 is similar to Mi, but the 
trigonid is larger, absolutely and relatively, and is as wide as or wider 
than the talonid. The entoconid is reduced in size, in height, and in 
distinction and the talonid basin more open. M3 is reduced, the 
trigonid decidedly the widest part of the tooth, the entoconid indis- 
tinct, and the hypoconulid large and sharply projecting as a well- 
defined spur. 

U.S.N.M. no. 9686 preserves dm4. Its talonid closely resembles 
that of Ml but is smaller. Tlie trigonid is much more elongate and 
narrow than on the permanent molars, and the paraconid is larger 
and well separated from the metaconid. 

The horizontal ramus is slender, with a long symphysis, which 
seems not to have fused even in old age. The posterior mental 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



237 



foramen is generally beneath the posterior end of P3 or anterior end 
of P4. The coronoid process seems to have been high and broad. 
The masseteric fossa is shallow and simple, its only sharp boundary 
anterior. The angle is poorly preserved but evidently was rounded 
and not sharply projecting. The dental foramen is about on a level 
with the alveolar border. The condyle is elevated well above the 
teeth and its transversely oval, gently convex articular surface faces 
equally posteriorly and superiorl3^ 

The infraorbital foramen is above P^, and the zj^goma arises chiefly 
above M^. 

The statistical constants of the principal tooth dimensions are given 
in table 51, based entirely on the sample from the Gidley Quarry. 

Table 51. — Numerical data on upper and lower dentition of Ellipsodon aquilonius 



Variate 



LP,- 
WP3- 
LP,.. 
WP4- 
LMi. 
WMi 
LMo_ 
WM2 
LM3. 
WM3, 
LP3__ 
WP^ 
LP<._ 
WPi. 
LML 
WM> 
LM2_ 
WM2 
LM3. 
WM2 



N 



10 
10 
10 

11 

19 

19 

28 

29 

24 

24 

6 

7 

7 

7 

10 

10 

13 

13 

8 

9 



R 



8-3. 5 
7-2. 1 
2-3. 7 
1-2. 5 
1-3. 6 
7-3. 2 
1-3. 9 
8-3. 6 
5-4. 1 
4-3. 
1-3. 3 
5-2. 9 
0-3. 2 
8-4. 1 
1-3. 4 
1-4. 5 
1-3. 7 
9-5. 4 
3-2. 6 
5-4. 1 



U 



3. 22 ±0.06 

1. SS±0. 03 
3. 41 ±0. 05 

2. 31 ±0. 04 

3. 40 iO. 03 

2. 90 ±0. 04 

3. 58 ± 0. 03 
3. 30 iO. 04 
3. 82 ±0. 03 

2. 75 ±0. 03 

3. 23 ±0. 03 

2. 71 ±0. 06 

3. 11 ±0. 024 
3. 96 ±0. 04 

3. 21 ±0.03 

4. 29 ±0. 05 
.3. 43 ±0. 05 

5. 20 ±0. 05 

2. 40 ±0. 04 

3. 71 ±0.07 



0. 19 ±0. 04 
0. 108±0. 024 
0. 16 ±0. 04 
0. 116±0. 025 
0. 143 ±0. 023 
0. 172 ±0. 028 
0. 179±0. 024 
0. 1 90 ± 0. 025 
0. 134±0. 019 
0. ]61±0. 023 
0. 075 ±0. 022 
0. 15 ±0. 04 
0. 064 ±0. 017 
0. 12 ±0. 03 
0. 104±0. 023 
0. 14 ±0.03 
0. 17 ±0.03 
0. 17 ±0. 03 
0. 100±0. 025 
0. 21 ±0. 05 



6. 0±1. 3 

3. 7±0. 8 

4. 6±1. 

5. 0±1. 1 

4. 2±0. 7 

5. 9±1. 
5. 0±0. 7 
5. 8±0. 8 
3. 5 ± 0. 5 
5. 8±0. 8 
2. 3±0. 7 
5. 4±1. 4 

2. 1±0. 6 

3. 0±0. 8 
3. 3±0. 7 

3. 4±0. 8 

4. 9±1. 1 

3. 2±0. 6 

4. 2±1. 

5. 6±1. 3 



Despite the fact that the sam.ple probably includes both sexes and 
certainly includes teeth in many different stages of wear, the figures 
are very consistent and show remarkably little variation. The high- 
est V is only 6.0 and the average is 4.35. The consistent distribution 
of the V's is also striking, for of the 20 values only two differ from 
the average by as much as twice the corresponding standard error. 
The two exceptions (for length of P^ and length of P^) are based on 
scanty data and are abnormally low values, 2.3 and 2.1. 

The unusually adequate sample of E. aquilonius from the Gidley 
Quarry and the presence of seven lower jaws apparently of the same 
species from the Silberling Quarry afford the best opportunity to 
detect any minor differences that might occur between these two 
horizons and localities. The possible association of morphological 



238 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

variants with one locality or the other and possible differences in 
mean dimensions have been carefully compared. The greatest differ- 
ence in mean dimensions is only 0.2 mm (for width of P3), wliich is 
not shown to be significant (it being mathematically demonstrable 
that a difference as great would arise in random sampUng of a homo- 
geneous sample about once in 20 trials or oftener). The other differ- 
ences are far from any probable significance. Only one specimen 
from the Silberling Quarry falls outside the observed range for the 
Gidley Quarry in a single dimension, having Mi 3.8 mm in length, 
but this is far within the probable range of the Gidley Quarry popu- 
lation, the deviation being only 1.4 times the standard deviation. 

It is unnecessary to give the results of the numerous other detailed 
comparisons made, since all were negative, showing no significant 
difference between the samples from the two quarries. Since the 
samples are so good, this warrants the positive affirmation that a 
single race of this species occurs in both quarries. 

A single specimen from Loc. 51, U.S.N.M. no. 9709, a lower jaw 
with Ml and broken M2, has these two teeth above the average size 
for the Gidley Quarry sample, but within the range of the latter. 

ELLIPSODON species 

U.S.N.M. no. 9662, from Loc. 18, is a partial right lower jaw with 
P4. This tooth resembles that of Ellipsodon aquilonius but is rela- 
tively higher, the paraconid is more distinct, and the length, 4.2 mm, 
is significantly greater than in that species (d/a-=4.9), although the 
width, 2.6 mm, is not (d/a-=2.5). Tliis is probably another species, 
but the material is inadequate for its exact determination. 

Genus LITALETES Simpson 

Litaletes Simpson, 1935d, p. 242. 

Type. — Litaletes disjundus Simpson. 

Distribution. — Middle Paleocene, Fort Union, Montana. 

Diagnosis. — P4 with bladelike main cusp, distinct paraconid and 
relatively large metaconid, talonid small with narrow, rudimentary, 
open basin. Molar paraconids distinct, small, internal. Entoconids 
indistinct, fusing with hypoconulids, especially on M2. P* with rudi- 
mentary metacone, strong metastyle. M^-^ with distinct hypocones. 
M^3 not reduced, M^ with strong metacone. 

Discussion. — This genus is very distinct from Ellipsodon, but 
Litaletes disjundus and Ellipsodon aquilonius do not differ very 
greatly. It could hardly be supposed that Ellipsodon inaequidens, 
type of that genus, is congeneric with Litaletes disjunctus, for their 
whole adaptive tendency seems different, and each tooth has definite 
and pronounced structural distinctions. The question then is not 
whether Ellipsodon and Litaletes fire distinct genera, but where the 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



239 



more or less transitional Ellipsodon aquilonius belongs. It is closer 
to Ellipsodon acolytus than to Litaletes disjundus or any other species 
known to me, and, as already stated, that is the reason for referring 
it to Ellipsodon at present. It is, however, probably closer to Lita- 
letes disjundus than to Ellipsodon inaequidens. Perhaps it will be 
necessary to transfer E. aquilonius and E. acolytus to Litaletes at some 
future time, but that introduces a great difficulty as regards the 
generic position of E. lemuroides, and for the present the system 
adopted here seems equally natural and more convenient. 

LITALETES DISJUNCTUS Simpson 

Figures 64, 65 
Litaletes disjundus Simpson, 1935d, p. 242. 

Type.— U.S. ISSM. no. 9323, right lower jaw with C-M3 (M3 broken). 
Collected by A. C. Silberling. 

Paratype. — U.S.N. M. no. 9324, right upper jaw with P^-M^ 
Collected by A. C. Silberhng. 

Horizon and locality. — Gidley Quarry, Fort Union, Middle Paleocene 
horizon. Crazy Mountain Field, Mont. 

Diagnosis. — Sole laiown species of genus. Measurements given in 
table 52. 

Discussion. — P^~* and M' of the species are now known only from 
the paratype, so that their variation is not established. On this 
specimen both P^ and P^ have distinct parastjde and metastyle and 
on both the posterior amphicone crest bears a rudimentary metacone, 
larger on P*. P^ has a rudimentary protocone. On P* the metaconule 
is not developed on the cingulum but more normally, on the protocone 
wing, and the cingulum does not cross the inner face of the protocone. 
On M^~^ the parastyle is unusually prominent and the hypocone is 
larger than in Ellipsodon aquilonius and not so near the protocone 
apex. M^ is less reduced, less oval, and the metacone, although 
smaller than the paracone, is large and distinct. 

Table 52. — Available numerical data on lower teeth of Litaletes disjunctus/rom the 

Gidley Quarry 



Variato 


N 


R 


M 


2(d) 2 


LP3 

WP3 


3 
3 
5 
5 
7 
5 
6 
5 
3 
4 


3. 3-3. 5 

1. 9-2. 1 
3. 5-3. 9 

2. 4-2. 8 

3. 9-4. 2 

3. 2-3. 5 

4. 3-5. 2 
3. 7-4. 5 

5. 0-5 3 
3. 3-3. 8 


3.37 
2.00 
3. 68 

2. 54 
4.07 

3. 30 

4. 67 

4. 04 

5. 13 
3. 55 


0. 0267 
0. 0200 


LP4 


0. 1080 


WP4 


0. 1120 


LM,._. 


0. 0743 


WMi .-- 


0. 0800 


LM2 


0. 5134 


WM2 


0. 3520 


LM3 


0. 0407 


WM3 


0. 1700 



240 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



,n^;:m/ 






Figure 6i.—Litaletes disjunctus Simpson: a, U.S.N.M. no. 9281, 
right P4-M3, crowTi view; 6, U.S.N.M. no. 9323, right lower 
jaw, external view; c, U.S.N.M. no. 9338, right lower jaw, 
internal view. Twice natural size. 





:Figure 65.—LUaletes disjunctus Simpson, U.S.N.M. no. 9324, 
right upper jaw: a, E.xternal view; 6, crown view. Throe 
times natural size. 



The lower canine is a 
small but tall, erect, spat- 
ulate tooth. Pi is low, 
l-rooted, with a minute 
heel. P2-3 are more ad- 
vanced than in Ellipsodon 
in that each has a distinct 
paraconid. The heel is, 
how^ever, relatively short, 
and only half its v/idth is 
formed by the incipient 
basin. The anterior blade 
of the protocone is dis- 
tinctively modified into 
a sort of shearing crest. 

The lower molars close- 
ly resemble those oi Ellip- 
sodon aquilonius, but Mi 
has trigonid and talonid 
of nearly equal width, 
M2 has trigonid generally 
markedly wider, and M3 
is less reduced. 

U.S.N.M. no. 6179 from 
Log. 51, includes an M2 
morphologically 3ompa- 
rable to this species and 
measuring 4.7 by 3.9 mm, 
near the means for the 
Gidley Quarry specimens. 
There is, however, an 
upper jaw with M^"^ from 
the same locality, dimen- 
sions given in table 53, 
that is morphologically 
very close to this spe- 
cies but notably smaller 
than the available Gid- 
ley Quarry specimens. 
Since, however, these are 
only two in number it 
cannot be assumed that 
a real difference exists. 
The greatest relative dif- 
ference, in length of M^ 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



241 



does not necessarily imply a coefficient of variation higher than 5 
on the hypothesis that a single species is present, and this is a very 
moderate degree of variation for one species. 

Table 53. — Measurements (in mm) of available upper teeth of Litaletes disjvuictus 



U.S.N.M. no. 


P3 


P' 


Ml 


M3 


M« 


L 


W 


L 


W 


L 


W 


L 


W 


,L 


W 


9324 (Gidley Quary) -... 

9582 (Gidley Quarry) 


3.4 


2.8 


3.3 


4.4 


3.9 


5.0 


4.6 
4.8 
4.0 


6.2 
6.5 
5.6 


3.G 
3.4 
3.1 


5.3 
5.6 


9660 (Loc. 61) ... 














5.1 



















Subfamily Hyopsodontinae Trouessart, 1879 ' 

Revised definition. — Paleocene and Eocene hyopsodontid condy- 
larths with P'*4 not inflated, generally moderate in size, cuspidate, 
somewhat molariform but never exactly so, P4 generally with a meta- 
conid and wide but imperfect talonid basin. Molar paraconids 
median to subinternal, not fusing with metaconids, entoconids dis- 
tinct and high, talonid basins closed. M^3 little or not reduced. 
M'~^ with definite hypocone, small in earlier and large in later forms, 
sharply distinct from tip of protocone. 

Remarks. — Aside from the type genus, I place here Oxyacodon, 
Litomylus, Litolestes, and Haplaletes v/ith some assurance, Protoselene 
and Haplomylus very doubtfully. Litomylus and Haplaletes represent 
the subfamily in the present collection. 

Genus LITOMYLUS Simpson 

Litomylus Simpson, 1935d, p. 243. 

Type. — Litomylus dissentaneus Simpson. 

Distribution. — Middle Paleocene, Fort Union, Montana. 

Diagnosis. — P4 trenchant, paraconid rudimentary, metaconid dis- 
tinct, separated from the protoconid by a small pit. Molar cusps 
rather bunodont but acute, paraconids reduced and median, M% 
Uttle reduced, hypoconulid of M3 sharply projecting. Hypocones of 
M^~2 relatively large and internal. M^ transverse, triangular. 

LITOMYLUS DISSENTANEUS Simpson 

Figure 66, 67 

Litomylus dissentaneus Simpson, 1935d, p. 243. 

r^/pe.— U.S.N.M. no. 9425, left lower jaw with P3-M3. Collected 
by A. C. Silberling. 

» "Hyopsodinae" in the original publication, but the emendation can hardly be claimed to change 
authorship. 



242 



BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



Horizon and locality. — -Gidley Quarry, Fort Union, Middle Paleocene 
horizon. Crazy Mountain Field, Mont. 

Diagnosis. — Sole known species of genus. Dimensions given ir 
table 54. 

Discussion. — This is the rarest of the four species of hyopsodontids 
in the quarry, but it is distinctive and fairly well known. 




Figure 66.—Litom.ylus dissentaneus Simpson, U.S.N.M. no. 9425, left lower jaw: a, Crown view; 6, internal 

view. Four times natural size. 




Figure 67.- 



-Litomylus dissentaneus Simpson, U.S.N.M. no. 9557, with tooth in outline from U.S.N.M. 
no. 9580, right M'-^: a, E.xternal view; 6, crown view. Four times natural size. 



No upper teeth anterior to P* are known, and P* is represented only 
by an uncharacteristic fragment. M^~^ have sharp, subequal, nearly 
conical paracone and metacone. The protocone is likewise sharp and 
smaller than in the other species of this group. The conules are large 
and equal. The external cingulum is sharp and even forming equal 
angulations, rather than distinct cuspules, at the parastylar and meta- 
stylar corners. There is no mesostyle. The hypocone is larger than 
in any known contemporaneous species and is quite distinct from the 
protocone and equally internal, but smaller. M^ is markedly trans- 
verse and is triangular, not rounded or oval, without a hypocone but 
with a sharp, distinct metacone. 

P 3_4 are long, low, narrow, trenchant teeth, unlike any others known 
in this family. Each has a rudimentary, median, basal paraconid. 
The talonids are poorly developed in each case and have only a single 
posteromedian cuspule and a very rudimentary posterointernal basin. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



243 



The sharp posterior protoconid crest bears a very sHght thickening or 
cuspule. The anterointernal region is somewhat excavated and has a 
cingulum below it. P3 has no metaconid, but P4 has a small papilla 
about halfway up the crown, and above and external to it, between it 
and the protoconid apex, is a small pit or pocket. 

The lower molars, wdth their acute, well-separated major cusps, 
resemble those of Oxyacodon. The paraconids are vestigial, forming 
a small shelf or crest connected with the anterior protoconid wing 
but not wdth the metaconid. On Mi this nearly reaches the inner 
border, on M2 it is submedian, and on M3 fully median. Protoconid 
and metaconid are of nearly equal size. The heels are well basined 
and the entoconids are sharp and distinct, nearly as high as the 
hypoconids and on Mi_2 larger and higher than the small hypoconu- 
lids. On M3 the hypoconulid is as high as the hypoconid and projects 
sharpl}^ posteriorly. 

Only five specimens, all from the Gidley Quarry, are recognized as 
of this species. Measurements are given in table 54. 

Table 54. — Individual measurements {in mm) of upper and lower denlition of 

Litomylus dissentaneus 



U.S.N.M. 


P3 


P4 


Ml 


Ma 


M. 


no. 


L 


W 


L 


W 


L 


W 


L 


W 


L 


W 


9425 -. 


3.3 


1.7 


3.5 


1.9 


2.9 
2.9 


2.4 
2.1 


3.0 
3.0 


2.7 
2.5 


3.2 

3.4 


2.2 


9318 - 


2.2 


9536. 


3.6 


1.6 


3.9 


1.7 









U.S.N.M. no. 



9557. 
9580. 



Ml 



3.2 
2.9 



W 



4.2 
3.9 



M» 



3.3 
3.2 



W 



4.7 
4.5 



M3 



Genus HAPLALETES Simpson 

Haplaletes Simpson, 1935d, p. 243. 

Type. — Haplaletes disceptatrix Simpson. 

Distribution.— Middle Paleocene, Fort Union, Montana. 

Diagnosis. — P4 not trenchant, with distinct paraconid and meta- 
conid and relatively large basined heel. Molars bunodont, cusps 
rather rounded and low. Paraconids reduced and median. M3 
somewhat reduced, hypoconulid of M3 slightly projecting, markedly 
less than in Litomylus. Amphicones of P^~* more rounded than in 
Litolestes. P* with rudimentary metacone. Upper molars rounded. 
Hypocones of M^~^ distinct, but smaller than in Litomylus. M^ less 
transverse and more rounded. 



244 



BULLETIN 169, UNITED STATES NATIONAL MUSEUM 



HAPLALETES DISCEPTATRIX Simpson 

Figures 68, 69 
Haplaletes disceplatriz Simpson, 1935d, p. 244. 

Type.— U.S.'^.M. no 9500, right lower jaw with P3-M3. Collected 
by A. C. Silberling. 

Paratype. — U.S.N.M. no. 9555, right upper jaw with P^-M^ Col- 
lected by Dr. J. W. Gidley. 




Figure 68. — Haplaletes disccptatrix Simpson, U.S.N.M. no. 9500, with parts in outline supplied from 
U.S.N.M. no.f9600, right lower jaw: a. Crown view; 6, internal view. Four times natural size. 




Figure 69. — Haplaletes disceptatrix Simpson, U.S.N.M. no. 9555, right upper jaw: a, E.xternal view; 
6, crown view; r , internal view. Four times natural size. 



Horizon and locality. — Gidley Quarry, Fort Union, Middle Paleo- 
cene horizon. Crazy Mountain Field, Mont. 

Diagnosis. — Sole known species of genus. Dimensions in tables|55 
and 56. 

Discussion. — This delicate little species is the smallest condylarth 
in the quarries, and only Litolestes includes smaller known species in 
this order. 



FORT UNION OF CFwAZY MOUNTAIN FIELD, MONT. 



245 



Table 55. — Principal available numerical data on lower dentition of Haplaletes 
disceptatrix, all from the Gidley Quarry 



Varinte 



LP3- 
WP3 
LP4. 
WP4 
LM, 
WM 
LM2 
WM 
LMn 
WM 



N 



R 


M 


1-2. 3 


2. 20 


3-1. 5 


1. 40 


5 


2. 5 


6-1.7 


1. 65 


4-2. 6 


2. 48 


1-2. 3 


2. IS 


4-2. 9 


2. 65 


3-2. 7 


2.51 


6-2. 9 


2. 80 


2-2. 4 


2.31 



S(d2) 



0. 0200 
0. 0200 


0. 0050 
0. 0276 
0. 0276 
0. 1350 
0. 1006 
0. 0800 
0. 0286 



Table 56. — Measurements {in mm) of the two available upper dentitions o/Hapla- 
letes disceptatrix, both from the Gidley Quarry 


U S N M no 


pa 


P» 


P« 


Ml 


M' 


M» 




L 


W 


L 


W 


L 


W 


L 


W 


L W 


L 


W 


9555 - 

9556 - 


L5 


1.1 


2.2 


2.1 


2.4 
2.2 


2.9 


2.4 
2.5 


3.2 
3.1 


2. 6 3. 7 
2. 9 3. 7 


1.9 


3.1 















P^ is a small simple tooth resembling an anterior lower premolar. 
P^ is peculiar in having a low and small but sharp and distinct proto- 
cone. P^~* resemble those of Litaletes in their rudimentary metacones, 
but the metastyles are less developed, and P"* has no metaconule. The 
upper molars are similar to those of Litomylus, but are more rounded 
in contour and have the hypocones of M^~^ smaller. 

P3 has a distinct paraconid and a heel about as well developed as that 
of P4 in most contemporaneous species. P4 has definite paraconid 
and m-ctaconid and a wide, large, basined heel with two posterior 
cusps. The lower molars resemble those of Litomylus, but the crowns 
are lower, the cusps blunter, and the internal cusps more distinctly 
elevated over the external. The talonid of M3 is less elongate. 

Family PHENACODONTIDAE Cope, 1881 

Most of the manuscript notes left hj Dr. Gidley refer to this group, 
and it was evidently his intention to publish a prehminary paper on 
it. There are three different drafts of part of his brief account, 
evidently written at different times and in part not consistent with 
one another. The draft that seems to be most recent is still mcom- 
plete and has still later memoranda written on it for other changes 
that were never made. The integral publication of this manuscript 
is impossible, as it does not form a connected whole and does not fairly 



246 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

represent the final opinions of Dr. Gidley. I have, however, quoted 
parts of the manuscript directly, have mentioned some other of Dr. 
Gidley's opinions in indirect quotation, and have used his manuscript 
names and followed his disposition of the specimens as far as possible. 

The material has been much increased since Dr. Gidley's study of 
it, but it is still rare. He tentatively identified only 8 specimens, and 
1 1 have since been collected (3 for the National Museum and 8 for the 
American Museum). This family is abundant in the Torrejon, and 
also in the lower Eocene, but it is extremely rare in the quarries in 
the Crazy Mountain Field and can be considered as common only at 
one surface locality, no. 25, from which 11 specimens have been 
obtained. 

In the Torrejon the only genus of this family is Tetraclaenodon} 
It is there very abundant and highly varied and has therefore received 
numerous specific names, but from Matthew's work it seems probable 
that only two valid species occur in the Torrejon: Tetraclaenodon 
jjuercensis, a larger, more common, and varied form, and T. pliciferus, 
a smaller, rarer, and perhaps less varied species. 

In the Crazy Mountain Field, also, there are indications of two 
species, one of about the size of T. puercensis, but very rare and not 
exactly identifiable, the other smaller, although generally larger than 
T. pliciferus. There is also a second genus, Gidleyina, apparently 
characteristic of the higher levels in this field. 

TETRACLAENODON Scott, 1892 

TETRACLAENODON SYMBOLICUS Gidley 

FiGUKES 70, 71 
Tetraclaenodon symbolicus Gidley, Simpson, 1935d, p. 239. 

Type. — U.S.N. M. no. 6169, part of right lower jaw wdth Mj and 
alveoh of P3.4 and M2. Collected by A. C. Silberling.^ 

Paratype. — U.S.N.M. no. 6168, jaw fragment with right Mi_2, and 
a separate left P4 probably this species but probably not associated. 
Collected by A. C. Silberling. 

' This genus is still often called Euprotogonia. It was originally described as Protogonia Cope, 1881. Cope 
later considered this as preoccupied by Protogonius Hiibner, 1816, and replaced it by Euprotogonia Cope, 
1893, the type of both being P. (or E.) subguadrata. In the meantime Scott had proposed the genus Tetra- 
claenodon Scott, 1892, for Mioctaenus floverianu-i Cope. Scott did not recognize the relationship, but his 
Tetraclaenodon was certainly the same genus as Protogonia Cope, and it therefore includes as a synonym 
Euprotogonia Cope. Matthew in 1897 preferred Euprotogonia Cope, 1893, to Tetraclaenodon Scott, 1892, on 
the ground that the latter was based on an error, and through Matthew's work Euprotogonia became the 
familiar name for the genus. Matthew later recognized that his action had been invalid, and he used the 
name Tetraclaenodon in all his more recent worls. Now Cabrera (1935) has insisted that Protogonius Hiibner 
does not preoccupy Protogonia Cope, since they differ in termination, and he calls the genus Protogonia. 
Without taking a decisive stand, I shall tentatively continue to use Tetraclaenodon, which has the cardinal 
virtue of being generally and correctly understood and of being unambiguous. Euprotogonia is certainly 
invalid, and Protogonia is of dubious validity, is ambiguous, and is unfamiliar to present-day students. 

' I retain this specimen as type, since it is clearly that intended by Qidley. No. 6168, here made paratype, 
would be a better type. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



247 



Horizon and locality. — Type from Silberling Quarry, paratype from 
Loc. 25, about 250 feet lower stratigrapliically, Fort Union, Middle 
Paleocene horizon, Montana. 




Figure 70. — Tttradaenodon symbolicus Qidley, 
U.S.N.M. no. 6169, right lower jaw (with Mj): a, 
Crown view; b, internal view. One and one-half 
times natural size. 




Figure ll.—Teiraciaenodon syinbolicus Gidley; 
a, U.S.N.M. no. 6168, right Mi_2, crown view; 
a', same internal view; 6, Princeton Univ. no. 
13757, right Ms-3, crown view. One and one- 
half times natural size. 



Diagnosis. — Gidley: "This species is smaller than E. [Tetraclaenodon, 
G. G. S.j puercensis, being about intermediate in size between that 
species and E. minor [= Tetraclaenodon pliciferus, G. G. S. ]. The 
lower molars are proportionately narrower transversely than those of 
the former species,* and the lower jaw is much shallower. This last 
character may be due in part, however, to a less mature condition of 
the specimen, which represents a young individual with the first true 
molar just coming into use.^ The striking similarity in detail of the 
lower molars with those of E. [T., G. G. S.l puercensis is a notable 
feature of the species and separates it clearly from E. minor [T, 
pliciferus, G. G. S.]. The more notable points of similarity are the 
slight roughening and wrinkling of the enamel surface and a tendency 
of the lophs of the teeth to break up into small cuspules." ^ 

Simpson: Intermediate between T. pliciferus and T. puercensis in 
size, but nearer the former both in size and in structure. The only 
constant difference from T. pliciferus is the greater size, inadequate 
for specific differentiation were it not constantly correlated with the 



* And within the range of T. pliciferus in this proportion.— O. O. S. 

• A specimen of T. pliciferus of comparable age has a deeper jaw, despite its smaller teeth but a referred 
specimen of T. symbolicus also has a deep jaw. This is probably a highly variable character, and also depends 
on crushing to a considerable degree.— Q. G. S. 

« From figures of the Torrejon specimens this would seem a striking and good distinction, but the speci- 
mens themselves show that T. pliciferus also has wrinkled enamel and a tendency for lophs to break up into 
cuspules. These may be functions of size, to a limited extent, and slightly less pronounced in T. pliciferus 
than in T. puercensis. T. symbolicus is about intermediate between the two in these characters, as in size. 

119212—37 17 



248 



BULLETIlSr 169, UNITED STATES NATIONAL MUSEUM 



widely different geographic distribution, as far as kjiown. Crenula- 
tions possibly slightly more developed and paraconid weaker on type 
and paratype of T. symbolicus, but these are variable characters and 
other specimens suggest that they are not of specific value. 

Discussion. — This species seems to be variable, and it is difficult to 
separate it from T. pliciferus, with which it must be closely related. 
Its smallest variants, indeed, could not be separated from T. pliciferus 
were they found together, but the homogeneous sample from Loc. 
25 averages larger than T. pliciferus. Since all these individuals are 
from one horizon and locality they evidently represent either one 
herd or an actually interbreeding stock, the character of which is thus 
slightly different from the Torrejon species and may be given taxo- 
nomic distinction. The size dift'erence is statistically significant. I 
therefore accept Dr. Gidley's species, but consider it as much closer 
to T. pliciferus than he believed. 

It happens that the type and to less degree the paratype have the 
enamel unusually crenulated and the paraconids small, characters 
slightly closer to T. puercensis than to T. pliciferus, although those 
species intergrade in this respect. The other specimens from Loc. 
25, however, have the enamel somewhat smoother and the paraconids 
more distinct, almost exactly as in T. pliciferus.'^ 

The more recently discovered specimens include one with dm4, 
representatives of all the lower molars and of P2 and P4, and also 
M^~^. These are all morphologically within the range of T. pliciferus. 
They might be grouped into three subdivisions, large, medium, and 
small, but I think the grouping would be subjective and that the 
variation is individual and approximately normal. 

Table 57. — Numerical data on lower molars of Tetraclacnodon sjmbolicus 



Variate 


N 


R 


M 


<T 


V 


LMi 


6 
6 
6 
6 
6 
6 


7. 4-7. 9 

5. 6-6. 6 
7. 5-8. 2 

6. 2-7. 

7. 3-8. 1 
5. 2-5. 7 


7. 63 ±0. 07 

6. 23 ±0. 13 

7. 77 ±0. 10 

6. 75 ±0. 12 

7. 70±0. 10 
5. 37 ±0. 08 


0. 18±0. 05 
0. 31 ±0. 09 
0. 24 ±0.07 
0. 30 ±0. 09 
0. 25 ±0.07 
0. 20 ±0. 06 


2. 4±0. 7 


WMi . 


5. 0±1. 4 


LM: _- 


3. 0±0. 9 


VVM2 


4. 5±1. 3 


LM3 

WM3 


3. 3±0. 9 
3. 8±1. 1 



The available material (including that in the American Museum) 
provides only six well-preserved examples of each of the three lower 
molars, and it is not entirely homogeneous since the type and one 
other specimen (as given below) are not from Loc. 25, whence all other 

» One of the most extreme specimens in this respect, U.S.N.M. no. 6167, was referred to T. symbolicus by 
Qiflley, in his notes, so that his conception of the species was the same as mine despite the differences in the 
diagnosis. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



249 



specimens were derived. Nevertheless the material is well unified, 
and data on it can be more adequately summed up in statistical form 
than otherwise. (Table 57.) 

The dimensions of the two specimens not from Loc. 25 are given 
in table 58. 

Table 58. — Individual measurements {in mm) oj lower molars of Tetraclaenodon 

symbolicus 



U.S.N.M. no. 


M, 


Mj 


Ma 




L 


w 


L 


W 


L 


w 


6169 


7.9 

7.5 


6.3 

6.6 






7.9 




9925 


5. 7 









These are to some extent marginal, as might be expected. The 
type, from the Silberling Quarry, has the largest Mi recorded, but a 
specimen from Loc. 25 approaches this within 0.1 mm. No. 9925, 
from Loc. 3, has the widest Mi and IM3 recorded, but these two dimen- 
sions are approached within 0.2 and 0.1 mm, respectively, by Loc. 25 
specimens. The variation is low for the whole series in any event, 
and there is no reason to believe it heterogeneous as to race. 

The close approach of this species to T. pliciferus is shown by the 
dimensions of Mi of the type of the latter, length 7.5, width 6, within 
the range of T. symbolicus but slightly below the mean. The most 
readily measurable of the types of T. "minor" == T. pliciferus, Amer. 
Mus. no. 3897, has the following dimensions: Length Mj, 6.8; width 
Ml, 5.6; length M2, 7.0; width Mo, 6.2. 

This is somewhat more representative of the smaller Torre] on 
species than is the type of T. plicijerus, which is a large variant. 
The lengths are below and the widths at the observed lower limits 
for T. symbolicus, and the differences are significant. 

Princeton no. 13757, from Loc. 9, one of the rare No. 1 Fort Union 
specimens, includes M^~^ evidently of Tetraclaenodon and closely 
comparable to T. symbolicus, although the variability of this species, 
lack of adequate material of the upper dentition, and some differ- 
ences from other specimens, perhaps individual and perhaps of minor 
taxonomic value, make the reference uncertain. 

TETRACLAENODON cf. PUERCENSIS (Cope, 1881) 

A few fragmentary specimens demonstrate the presence of a larger 
species of Tetraclaenodon. These include a left upper M^ from the 
Gidley Quarry (U.S.N.M. no. 9620), associated left dm^ and M^ 
from Loc. 6 (American Museum), associated left M^ and part of 



250 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

M^ from Loc. 82 (American Museum), and specimens figured by 
Douglass (1902b, p. 222) from Loc. 5 or 6. These specimens vary- 
considerably among themselves, and they are not clearly distinguish- 
able from variants of T. puercensis, but they are inadequate for 
specific determination and do not definitely establish the presence of 
that species in this field. 

The original of Douglass' 1908, pi. 1, fig. 4, is perhaps a right P^ 
of this same form, but this is uncertain, and the other isolated teeth 
referred to Tetraclaenodon by Douglass seem still more dubious. 

There are also preserved with U.S.N.M. no. 11913 a right and a 
left M^ (possibly M^) probably of Tetraclaenodon and, at least in their 
worn condition, closely resembling T. puercensis. They certainly are 
not associated with no. 11913, since they are from a much older indi- 
vidual, and it is very improbable that they are of the same species, 
and not at all clear that they are congeneric. No. 11913 is recorded 
as from Loc. 11 or 13. These localities are at about the same level 
and are the highest that have yielded identifiable mammals. A note 
by Silberling with the specimens seems to leave little doubt that 
these specimens were derived from that level except in the highly 
improbable case that they have accidentally been substituted for 
two other upper molars in the collection.* Tetraclaenodon has not 
otherwise been reported from beds as late as this, and these teeth 
are inadequate to establish its presence although they make it 
probable. 

Genus GIDLEYINA Simpson* 
Gidleyina Simpson, 1935d, p. 240. 

Type. — Gidleyina montanensis (Gidley). 

Distribution. — Upper Paleocene, Fort Union, Montana. 

Diagnosis. — Gidley '°: "Cheek teeth bunolophodont; first and sec- 
ond upper molars subquadrate, consisting of four principal cusps, 
two intermediates, and a well-developed mesostyle, conules con- 
nected by continuous lophs with the summit of the protocone; pre- 
molars 3 and 4 with well-developed protocones, but with metacones 
rudimentary; thus superficially they each consist of two principal 
transversely placed cusps." 

8 The teeth themselves are not mnrked, as are most specimens in the collection. 

• In one draft of his manuscript Dr. Gidley referred the type of this genus to Euprotogonia, in another 
to Ectocion, and in a third, presumably the most recent, to Proedocion, new genus. His new generic name 
is, however, preoccupied by Proectocion Ameghino, 1904, and therefore it cannot be used. He intended 
to change it, for he had made a pencil notation, "change name, not related to Ectocion, but rather to Pro- 
togonodon", but I find no other name in his notes or on his labels and so have been forced to supply one. 
It is highly appropriate that the genus should be named for Dr. Gidley. (Oidleya Cossman, 1907, is a fossil 
bovid.) 

>" Quoted from what is probably the most recent draft of Dr. Gidley's manuscript, the only one in which 
a new genus is proposed. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 251 

Simpson: Closely resembling Edocion, but upper premolars with 
much smaller metacones, first and second molars with slightly smaller 
mesostyles and hypocones, protoconules of P^~* and M^"^ slightly 
more united by lophs to protocone. 

Discussion. — The molars of this genus can hardly be distinguished 
generically from Edocion, although unlike any known species in 
details. The prem^olars, however, are distinctly less molariform and 
at once distinguish Gidleyina from Edocion. It is well known that 
from partial dentitions alone it is often difficult or impossible to 
determine even the ordinal affinities of genera in these ancient faunas, 
but in this case every indication is that Gidleyina is in fact related to 
Edocion, and perhaps ancestral to it." 

If this is correct, it is clear that the Edocion line was already distinct 
from that of Phenacodus in the Middle Paleocene and had already 
acquired a mesostyle and slightly more lophiodont pattern, although in 
other respects, such as the complication of the premolars, not more 
advanced than Tetraclaenodon}^ 

Among Torrejon genera, Gidleyina most closely resembles Pro- 
toselene in many respects but is at once distinguished by the large and 
posterointernal protocone on P^, distinct conules on P*, and other lesser 
details, suggesting that the relationship is not very close. The dis- 
tinctions from Protoselene are resemblances to Edocion. 

In addition to the type, based on an upper jaw, I tentatively 
refer two species based on lower jaws to this genus. They are 
described below. 

GIDLEYINA MONTANENSIS (Gidley) 

Figure 72 

Gidleyina montanensis (Gidley) Simpson, 1935d, p. 240. 

Type. — Princeton no. 12048, part of left maxilla with P^-M^ and a 
probably associated right P^. 

Horizon and locality. — Loc. 68, about 1,000 feet above Gidley 
Quarry, Fort Union, Sweetgrass County, Mont.^^ 

»i This is Dr. Qidley's opinion in all three drafts of the manuscript on this form, but still later he noted 
that affinity is closer with Protogonodon. This seems to me highly improbable and was perhaps noted 
rather as a point to check than as a conclusion. 

" In one of his manuscripts Dr. Gidley proposed placing the Tetradaenodon-Phenacodus and the Gidleyina- 
Eciocion phyla in different subfamilies. Even if we grant that the phyla were distinct from Middle Paleo- 
cene to lower Eocene, they are so similar that considering them as two subfamilies seems to me dispropor- 
tionate to the classification of other groups of mammals. 

" There are now no locality data with the specimen. One of Dr. Gidley's manuscripts says "Near sec. 
23, R. 15 E., T. 5 N. . . near top of Fort Union No. 2 of Silberling." Localities 4, 52, and 54 are the only 
ones in (or near) this section— the Gidley Quarry and a nearby exposure near the same level. As far as I 
can determine, no Princeton material came from anywhere near here. Another of Dr. Gidley's drafts, and 
apparently the latest, says "From the vicinity of Bear Butte. . . . Exact level not known, but probably 
from near the middle of the section of this locality." Mr. Silberling, however, remembers the discovery 
of the specimen and positively states that it was found at the locality now numbered 68. Two other speci- 
mens perhaps of this species are from the cluster of localities in the western part of T. 5 N., R. 15 E., where 
most of the Princeton specimens were found, some 1,500 feet above the base of No. 3. 



252 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

Diagnosis— Gidlej'' "P^ to M^^SH- mm; NP-^^lS.l mm; length 
of M' = 6.4 mm, greatest width=9.1 mm, width across hypocone and 
metacone=8.3 mm, greatest width of M^=9.8 mm, other measure- 
ments of this tooth same as those of M^; parastyle and mesostyle 
prominent, mesostyle angular and continuous with the ectoloph; P^ 
with uninterrupted internal cingulum, and with low but well-defined 
lophs connecting the summit of the protocone with the protoconule 
and base of the metacone respectively." 




Figure 72.— Gidteyina montanensis (Gidley), Princeton Univ. no. 12048, left upper jaw: a, External view; 
6, crown view. One and one-half times natural size. 



Discussion. — The P^ probably associated with the type is a simple 
2-rooted tooth with one laterally compressed external cusp, somewhat 
anterior on the crown, and a small posterointernal expansion of the 
base but not true protocone. 

My measurements of the type are as follows: P^-IVP, 19.6; M^~^, 
13.8; length P^, 4.5; width P^, 3.1 ; length P^ 5.9; width P^, 5.8; length 
PS 5.7; width V\ 7.2; length M', 7.0; width M^, 9.0; length M-, 
6.9; width M^, 9.9. 

Two other specimens from the same cluster of localities all at about 
the same level are in the Princeton collection. Princeton no. 14195 
is an M^ similar to that of the type but slightly larger and with the 
hypocone more internal. These could be individual variations. 
Princeton no. 14190 is an isolated P4 7.2 mm in length and 4.8 mm in 
width. Its size is almost exactly that of the corresponding tooth of 
?G. silberlingi, but the protoconid and metaconid are closer to each 
other and the metaconid is relatively more posterior. 

'* I quote Dr. Gidley's diagnosis from the draft in which he placed the species in a new genus. His other 
two diagnoses view it as a species of Tetraclaenodon and of Ectocion, respectively, and are therefore inappro- 
priate. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 253 

7GIDLEYINA SILBERLINGI (Gidley) 15 

Figure 73 

IGidleyina silherlingi (Gidley), Simpson, 1935d, p. 240. 

2VP6.— U.S.N.M. no. 6166, partial left lower jaw with P3-M3. 
Collected by A. C. Silberling. (In the same lot are a partial right 
lower jaw with M2-3 and another right lower jaw fragment with M2 
and the heel of Mi. They probably belong to the same species but 
include parts of one or two different individuals and are excluded from 
the type material.) 

Horizon and locality. — Loc. 27, about 400 feet above the base of 
Fort Union No. 3, Wheatland County, Mont.'*^ 

Diagnosis. — Gidley: " ... About the size of or a little smaller 
than E. minor [= Tetraclaenodon pliciferus, G. G. S.] . . . Jaw rela- 
tively long and slender, especially anteriorly; the teeth proportionately 
narrow transversely . . . with a decided tendency to selenodonty 
. . . The paraconid in the molars is vestigial or wanting, and P4 is 
submolariform . . . the heel . . . having the crescentic form of that 
of the molars, while the metaconid is large and as high as the 
protoconid." 

Discussion. — It is possible that this is the lower dentition of Gid- 
leyina montanensis. Since, however, it cannot be demonstrated to 
belong even to this genus and since among lower dentitions it is a 
distinctive and interesting type that requires some means of reference 
until its association with upper teeth can be established, it seems quite 
proper to accept Dr. Gidley's decision to define it as a species, which 
can be reduced to synonymy later, if necessary, with no great con- 
fusion. 

In comparison with other known low^er jaws, this is generically dis- 
tinct from any previously described. Ectocion is similar but has a 
simple longitudinal crest on P3, instead of an incipient crescent, while 
P4 is more complicated and molariform, with a distinct posterointernal 
cusp absent in the present specimen. The molars offer no contrast 
definitely of generic value, unless it be the somewhat larger and more 
definitely closed trigonid basins and less distinct vestigial paraconids 
of IGidleyina silherlingi. The possibility that Gidleyina is not really 
ancestral to Ectocion or, on the other hand, that ?6r. silberlingi does 
not belong to Gidleyina is enhanced by the fact that whereas the upper 

" In a draft of the manuscript on this family, Dr. Gidley describes this as a species of Euprotogonia 
(= Tetraclaenodon) . On the specimen label he has crossed out "Euprotogonia" and written "Ectocion." It is 
thus evident that he recognized the probable relationship of this jaw to the new genus I have named Gid- 
leyina, since this was also successively identifled by Dr. Gidley as Euprotogonia and as Ectocion before its 
generic distinction was recognized. I have not quoted his diagnosis in full, giving only enough to validate 
his claim to authorship of the species, since it was written before he had recognized the genus here named 
Oidleyina and therefore is not fully apropos. My comparisons following the diagnosis suffice for the expres- 
sion of more fully studied opinion as to diagnosis and affinities. 

" Given on labels, etc., as "Sweetgrass County", but, as can be seen on the map, this is one of several 
localities slightly north of the county line. 



254 



BULLETIN 169, UNITED STATES NATIONAL MUSEUM 



teeth of Gidleyina montanensis are almost ideally prototypal to those 
of Edocion, the lower teeth called W. silberlingi seem to be progressing 
either more rapidly or in a different direction in the development of 
P3 and the molar trigonids. This is not certain, however, as these 
characters are highly variable and an apparent reversion of this sort 
is not inconceivable. 




Figure Ti.—'iQidleyina silberlingi (Qidley), U.S.N.M. no. 6166, left lower jaw: a, Crown view; 6, external 
view. One and one-half times natural size. 



P3 differs markedly from that of Tefraclaenodon in its incipient cres- 
cent and basin, but P4 is basically similar. The molar paraconid is 
much less distinct in ?G. silberlingi than in most specimens of Tetra- 
claenodon, although approached by a few extreme variants of the 
latter, and the enamel is much less rugose, the crests less crenulated. 
These characters suggest Protoselene, but in the latter even P4 is much 
less molariform, with the metaconid strong in ?6^. silberlingi, barely 
incipient at best and the talonid very different. 

The following measurements are from the type: Length P3, 6.7; 
width P3, 3.9; length P4, 7.2; width P4, 4.7; length Mi, 7.0; width 
M„ 5.4; length M2, 7.3; width M2, 5.4; length M3, 7.3; width, M3, 4.6. 

TGIDLEYINA SUPERIOR (Simpson) 

Figure 74 

7 Tetraclaenodon superior Simpson, 1935d, p. 239. 

Type. — U.S.N.M. no. 11913, part of left lower jaw with talonid of 
Ml, M2, and M3 still in capsule. Collected by A. C. Silberling.^^ 

Horizon and locality. — Loc. 11 or 13, about 3,000 feet above the base 
of Fort Union No. 3, Sweetgrass County, Mont. 

Diagnosis. — Lower molars with paraconids vestigial, broad trigonid 
basins with crenulated anterior margin, crenulations otherwise slight. 

•' The two upper molars apparently of Tetraclaenodon, discussed on a previous page, are preserved in the 
same lot of material but are not associated with the lower jaw and were definitely excluded from the type 
material of this species. 



FOKT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



255 



External cingulum absent, talonids incipiently lophoid. Talonid of 
M2 markedly narrower than trigonid. Lower molars of about the size 
of those of Tetraclaenodon symhoUcus but slightly narrower relatively. 
Somewhat longer and distinctly wider than those of 1G. silberlingi. 
M2 length 7.7, trigonid width 6.2, talonid width 5.5. 




Figure 7i.—'!Gidteyina superior (Simpson), U.S.N.M. uo. iiyid, leu lower jaw: o, Crown view; 6, internal 
view. One and one-balf times natural size. 



Remarks. — This distinctive but imperfectly known species was at 
first referred, with a query, to Tetraclaenodon, but with the comment 
that it might belong to Gidleyina. The crucial evidence of the pre- 
molars is lacking, but after further study it seems probable that it is 
congeneric with IGidleyina silberlingi. The relatively slight enamel 
crenulation, the structure of the trigonids, and the incipiently lophio- 
dont talonids are distinctions from species surely referred to Tetra- 
claenodon and points of resemblance to ?6^. silberlingi. Reference to 
Gidleyina depends on that of the last-named species, discussed above. 

Family PERIPTYCHIDAE Cope, 1882 
Subfamily Anisonchinae Osbom and Earle, 1895 

Anisonchines are among the commonest fossils in the Puerco and 
Torrejon, but in the present fauna they are neither abundant nor 
varied. One form cannot at present be distinguished from the 
Torrejon species Anisonchus sedorius. Only one other form, Cori- 
phagus montanus, is recognized. This genus also occurs in the Torre- 
jon, but the species is distinct. The recognition that Mixoclaenus 
is a synonym of Coriphagus and that these animals are not oxy- 
claenids, as generally supposed, but primitive anisonchines clears up a 
decided taxonomic anomaly and also casts important light on the 
origin and affinities of the Anisonchinae. 

The five genera of tliis subfamily so far distinguished may be recog- 
nized by criteria presented in table 59. 



256 



BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 





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FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 257 

Genus CORIPHAGUS Douglass 

Coriphagus Douglass, 1908, p. 17. 

Mixoclaenus Matthew and Granger, 1921, p. 7. 

Type. — Coriphagus montanus Douglass. 

Type of IMixoclaenus. — Mixoclaenus encinensis Matthew and 
Granger. 

Distribution. — Middle Paleocene, Fort Union, Montana, and Torre- 
jon, New Mexico. 

Diagnosis. — Pi 1-rooted. P3-4 subeqiial, somewhat swollen but 
elongate, with minute anterior basal cusps and small heels basined 
posterointernaliy. Molars relatively small, trigonids larger than talo- 
nids and notably higher, paraconids distinct and nearly internal, 
trigonids basined with cusps crested, poorly differentiated, and not 
conical. M3 much reduced, with hypoconulid distinguishable but 
not prominent. P^ with very rudimentary protocone, P* with dis- 
tinct but small subcorneal protocone, M^~^ transverse, subquadrate, 
outer borders angulate and emarginate, distinct hypocones postero- 
internal to protocones and on cingula nearly enveloping the latter. 

Discussion. — Douglass based this genus and its type species on a 
single but unusually complete lower jaw with P2-M3, found by Silber- 
Hng in the Silberling Quarry. In 1913 and 1916 parties under Dr. 
Granger found three '^ specimens of a similar form in the Torrejon, 
and in 1921 Matthew and Granger described these as Mixoclaenus. 
They then noted the resemblance of Mixoclaenus to Coriphagus 
but cannot have realized, from Douglass' somewhat schematic figure, 
how close it is. They decided to hold Mixoclaenus as distinct at least 
until discovery of the upper dentition of Coriphagus. Matthew's 
fuller description of Mixoclaenus (Pale. Alem.) was written before 
1921 (probably in 1917) and was not corrected. It does not mention 
the resemblance to Coriphagus. The upper dentition of Coriphagus 
montanus is now partly known, and it has been possible to compare 
original specimens of that species and of Mixoclaenus encinensis. The 
conclusion is that the two species are unquestionably congeneric and 
hence that Mixoclaenus is a synonym of Coriphagus. They compare 
very closely in every known part, and the type species of the two 
supposed genera differ only in size and doubtfully in sUght variations 
of proportions. 

Douglass (1908) referred Coriphagus to the ?Insectivora, without 
family assignment. Matthew and Granger (1921) placed '^Mixo- 
claenus^' in the Oxyclaenidae but noted resemblances to Mioclaeninae 
and Anisonchinae.^^ In his longer work Matthew (Pale. Mem.) has 

'8 Matthew mentions four, describing only two of them, but I can only find three in the collection. 

" Hay (1930) followed them in placing Mixoclaenus (which he wrongly ascribed to the Tiflany) in the 
Oxycla/snidae, but he placed Coriphagus in the Plagiomenidae, a family with which it has practically nothing 
in common. Schlosser (1923) placed Aliioclaenus (which he wrongly ascribed to the Puerco) in the Oxy- 
claenidae and Coriphagus in the Mioclaenidae. These and other casual references are accompanied by no 
evidence and require no discussion. 



258 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

outlined the evidence in more detail. (He is discussing Mixoclaenus, 
which now proves to be Coriphagus.) The only oxyclaenid character 
given is "upper molars resembling those of Chriacus", but he adds 
that they are wider transversely, more triangular, external angles 
more prominent,^" hypocone less so, and M^ much reduced and more 
transverse. With these, and other modifications, the resemblance to 
Chriacus is really quite attenuated. Matthew notes that the rounded 
condyle and other characters of the jaw and the small premolariform 
canine are not oxyclaenid but do not approach condylarths or in- 
sectivores. I add that they do, almost to identity, approach the 
Anisonchinae. Matthew also notes, but rejects as inconclusive, some 
resemblance to Didelphodus, leptictids, and Palaeosinopa in the molars, 
but adds that the premolars suggest the Mioclaeninae but are more 
like the Anisonchinae. 

This genus has, in fact, all the diagnostic characters of the Anison- 
chinae and nothing that decisively indicates pertinence to any other 
group. The upper and lower premolars are of fully anisonchine type 
and are especially suggestive of Conacodon cophater.^^ They differ 
in such details, well within the morphological range of the Anison- 
chinae generally, as the incipient development of a protocone on P^ 
and the less transverse P*. This last tooth is intermediate between 
the "round premolar cusp" type (Hemithlaeus and Conacodon) and 
the "flat premolar cusp" type {Haploconus and Anisonchus), adding 
to the evidence already given by Matthew that these are not, as 
Osborn and Earle thought, major phyletic divisions of the Anison- 
chinae. The lower premolars still more closely resemble those of 
Conacodon cophater, the only definite differences being that they are 
shghtly less inflated and have the anterior basal cuspule a little smaller 
(but larger than in Conacodon entoconus). Matthew (Pale. Mem.) 
mentions the heavy and pecuHar wear on these teeth in Coriphagus 
{^^ Mixoclaenus^'), truncating them obhquely. This wear occurs in all 
Anisonchinae and is almost diagnostic of the group. 

The molars are on the whole more primitive or generalized than 
those of other anisonchines, which is what induced Matthew to refer 
the genus to the Oxyclaenidae. Yet they have the basic anisonchine 
characters. The upper molars markedly resemble those of Anison- 
chus gillianus and Conacodon cophater, apparently the most primitive 
in this respect among other anisonchines. From the former they 
differ chiefly in the less rounded outer contour, shorter internal slope, 
and development of the hypocone on a cingulum around the protocone. 
The first and last of these characters are resemblances to Conacodon 
cophater in which, however, the internal slope is also long and the hypo- 
cone is more internal, with respect to the protocone, than in Cori- 

"> This does not seem to me to be quite certain. • 

" Conacodon entoccnus differs greatly from tiie smaller species and might almost be distinguished from it 
generically. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 259 

phagus. M^ is markedly reduced and very transverse, a resemblance 
to Conacodon cophater but here somewhat intensified. 

In the lower molars the large swollen trigonids with the tips of the 
cusps pinched together, giving an aspect difficult to describe but 
characteristic when seen, is diagnostic of Anisonchinae and typically 
developed in Coriphagus. The paraconids are retained and are closely 
similar to those of Anisonchus gillianus, possibly a trifle more internal, 
but hardly more so than in some specimens of that species; in A. sec- 
torius they are more definitely median. The molar talonids are rela- 
tively smaller and their cusps less conical and distinct, especially on 
M3. This is perhaps the most aberrant feature of Coriphagus, con- 
sidered as an anisonchine, but the difference from such a form as 
Conacodon cophater is really slight. 

The characters of the mandible mentioned or shown by Matthew are 
almost identical with those of other anisonchines about the same size. 

Coriphagus is in many respects the most primitive known anison- 
chine, representing, in view of its age, an unprogressive surviving type. 
Its closest comparisons are with Conacodon cophater and Anisonchus 
gillianus, both Puerco species and older than the known species of 
Coriphagus. Coriphagus carries still closer the marked resemblance 
already noted between the anisonchine and the hyopsodontid denti- 
tions. Were no other anisonchines known, it could very well be classed 
as a hyopsodontid representing another incipiently divergent line in 
addition to the several already known in that group. But all these 
divergent characters are in the direction of the more specialized anison- 
chines, and these in turn show marked resemblance to the still more 
specialized periptychines. The whole hyopsodontid-periptychid com- 
plex seems to bear the definite stamp of divergence from a common 
ancestry. 

CORIPHAGUS MONTANUS Douglass 

Figures 75, 76 

Coriphagus montanus Douglass, 1908, p. 17. 

Type. — Carnegie Mus. no. 1669, left lower jaw with P2-M3. Col- 
lected by A. C. Silberling. 

Horizon and locality. — Type from Silberling Quarry, several referred 
specimens from Gidley Quarry, Fort Union, Middle Paleocene horizon, 
Crazy Mountain Field, Mont. 

Diagnosis. — Smaller than C. encinensis (see measurements). Lower 
teeth relatively narrow. M3 less reduced relative to other teeth. 

Discussion. — The differences in proportions given are not entirely 
certain, since they depend on only one specimen of C. encinensis, and 
these characters are variable. The size difference is slight and in 
itself might not warrant full specific status, but its constant association 
with different provenience makes it certainly significant. Every di- 



260 



BULLETIN 169, UNITED STATES NATIONAL MUSEUM 



mension of all three specimens of C. encinensls is larger than the cor- 
responding dimension of any of the seven available specimens of 
C. montanus. The best single comparison is of the length of Mi, which 
compares as follows, by Fisher's formula: 

LM„ C. monlanus: N 6 M 3.25] ^ ^ p ^^^ 

LMi, C. encmensis: N 2, M 3.70J 




FiGTJEE 75.— CorJpftaffMS montanus Douglass, U.S.N.M. no. 9334, with parts in outline supplied from 
U.S.N.M. nos. 9599 and 9685, left lower jaw: a, Crown view; b, internal view. Four times natural size. 

The difference is certainly significant although not great. ^^ 
Table 60 gives ranges and means for the National Museum speci- 
mens of C. montanus and corresponding dimensions of the paratype of 
C. encinensls, Amer. Mus. no. 17074. The material is not sufficiently 
abundant for the calculation of other statistical constants. 

Table 60. — Numerical data on lower dentition of Coriphagus montanus and C. 

encinensi.s 



Dimension 



WP,-.. 
LP4... 
WP4— 
LMi... 
WMi.. 
LM2_.. 
WMj.. 
LM3_-. 
WM3-. 
LMi_3- 





C. montanus 




C. encinensu 








(Paratype) 


N 


R 


M 




3 


2. 7-2. 8 


2. 77 


3. 2 


3 


1. 4-L 7 


1. 53 


2. 1 


2 


2. 3-2. 5 


2. 40 


3. 1 


2 


1. 4-1. 6 


1. 50 


2. 3 


6 


3. 1-3. 5 


3. 25 


3.7 


6 


2 1-2 2 


2. 13 


2.8 


6 


2. 5-2. 9 


2. 72 


3.4 


6 


2. 0-2. 4 


2. 18 


2.8 


3 


2. 3-2. 8 


2. 60 


2.9 


3 


1. 7-1. 9 


1. 80 


2. 2 


2 


8. 2-8. 7 


8. 45 


9.9 



'J The mean of C. encinensls is only 14 percent greater than for C. montanus, and it is to be stressed that this 
is not in itself and stated in this way of specific value. The largest specimen of C. montamis is 13 percent 
greater than the smallest, and the paratype of C. encinensls is only 6 percent larger than the largest of our 
specimens of C. montanus in this dimension. With large series the two species would doubtless intergrade 
in size, yet they are certainly distinct. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 261 




Figure 76. — Coriphagus montanus Douglass, U.S.N.M. no. 9591, left upper jaw, crown view. Four times 

natural size. 




Figure 77.— ^4nwo7icAM* sectonus (Cope), referred specimen from the Lebo, U.S.N.M. no. 9267, right lower 
jaw: a, Crown view; 6, external view. Twice natural size. 




Figure 7&.—Anisonehus sedorius (Cope), referred specimen from the Lebo, U.S.N.M no. 92i"3, right upper 
jaw: a. External view; b, crown view. Twice natural size. 



262 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

U.S.N.M. no. 9591 is a left upper jaw with P^-M^ and about half 
of M^, from the Gidley Quarry, which is certainly referable to Cori- 
phagus montanus. It is deeply worn but well shows the generic 
characters. P^ may be slightly less transverse and the external 
cingulum of P* weaker than in C. encinensis, and all the teeth are 
slightly smaller, but the agreement in structure is very close. 

Genus ANISONCHUS Cope, 1881 

ANISONCHUS SECTORIUS (Cope, 1881) 

Figures 77-79 

Douglass (1902b, p. 222) described and figured an Anisonchus that 
he compared with A. sectorius but mentioned the possibility that it 
might be distinct. The National Museum collection includes a series 
of excellent specimens of this genus, and their pertinence to Anisorichus 
sectorius can be rather positively estabUshed, although they may well 
pertain to local races as will be pointed out.^^ 

Anisonchus is the only genus represented by good material in this 
fauna that seems to be represented here by the same species as that 
occurring in the Torrejon. It therefore is a special point of attack 
for considering the relationships of these two widely separated Middle 
Paleocene deposits, and the material has been subjected to detailed 
and lengthy analysis. The results are not entirely conclusive, largely 
owing to the small size of the available pure samples, but they nsver- 
theless are of considerable interest, and they also provide data that 
must be useful in future work. The full analysis would fill many 
pages with numerical and morphological data and calculations, and 
so it is not published here in extenso, but only such figures as are most 
necessary to illustrate the general conclusions reached. 

A study was first made of the Torrejon specimens themselves to 
see whether more than one species or race could be distinguished, par- 
ticular attention being paid to possible distinction between material 
from the two principal fossil levels of the Torrejon. The results of 
this analysis were negative: From the data at hand it is not possible 
to subdivide the Torrejon material, all of which is referable to Anison- 
chus sectorius.^* Despite considerable variation, there is only one 
specimen, Amer. Mus. no. 3533, that stands out as strongly aberrant. 
It was collected by Baldwin in 1885, and the exact horizon and locality 
are not recorded. Even this specimen, however, is so close to typical 
A. sectorius that it would be methodologically incorrect to discard it 
from the general sample. 

« Labels show that Dr. Gidley referred some of the Fort Union specimens to Anisonchus sectorius and 
some to a new species, but he loft no diagnosis or discussion. I have carefully endeavored to visualize his 
concept of the new species, thinking that it might correspond with one of the inconclusively indicated local 
races, but this does not seem to be the case, and I am unable to ascertain the characters relied on by him. 

" It may be noted, however, that Matthew is incorrect in believing one of the cotypes of A. 7nandibutaTis 
to belong to Anisonchus sectorius. Whatever the position of this very dubious species, it is not a synonym 
of A. sectorius and probably does not belong in Anisonchus. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



263 



The general statistical data on the simple dimensions of the lower 
teeth of all Torrejon specimens of Anisonchus sectorius in the American 
Museum are presented in table 61. 

Table 61. — Numerical data on lower dentition of Anisonchus sectorius 



Variate 


N 


R 


M 


<T 


V 


LPs 


8 
8 
17 
17 
17 
17 
21 
23 
14 
14 


5. 8-6. 8 

2. 8-4. 1 
5. 3-6. 6 

3. 5-4. 3 
5. 0-5. 8 

3. 5-4. 2 

4. 8-5. 6 
3. 7-4. 4 

5. 1-6. 1 
3. 2-4. 


6. 28±0. 11 
3. 22 ±0. 14 
5. 86 ±0. 07 
3. 88 ±0.05 
5. 47 ±0. 05 

3. 87 ±0. 04 
5. 34 ±0.04 

4. 06±0. 03 

5. 58 ±0.08 
3. 54 ±0.05 


0. 30 ±0.08 
0. 40±0. 10 
0. 30 ±0.05 
0. 22 ±0. 04 
0.22 ±0.04 
0. 17 ±0.03 
0.20 ±0.03 
0. 17 ±0.02 
0.28 ±0.05 
0. 20 ±0.04 


4 8± 1 2 


WPs 

LP* 


12. 3 ±3. 1 
5. 2±0. 9 
5. 7±1. 
5. 7±1. 
4. 5±0. 8 
3 8±0 6 


WP4 

LM, 


WM, 

LMj 


WM, 

LM3 

WM3 


4. 1±0. 6 

5. 0±1. Q 

5. 7±1. 1 



The lower dentition material from the Crazy Mountain Field now 
available consists of three specimens from the Gidley Quarry, three 
from Loc. 25, four from Loc. 51, and one each from Locs. 50 and 18. 
The highest number of comparable specimens from a single horizon 
and locality is only three, for P4 from the Gidley Quarry. 



10- 



"> 

'13 

c 



4.9 



— I — 
5.2 



5.5 5.8 



— I — 

6.1 



LENGTH Ml 



Figure 79.— Histogram of the length of Mi In Anisonchus sectorius (Cope): In solid outline, Torrejon speci- 
mens (American Museum); in dotted outline, Lebo specimens (National Museum). 



By inspection of the specimens and of their dimensions, it is sug- 
gested that there is local differentiation. Thus in the series from the 
Gidley Quarry, Loc. 25, and Loc. 51, each local sample seems to be 
reasonably homogeneous and to differ slightly from that of the other 
two localities. In the jaws from the Gidley Quarry the lower molars 
are longer, but not noticeably wider, than those from Loc. 25. The 
very poor material from Loc. 51 suggests closer agreement mth the 
Gidley Quarry at least in P4 and Mj, but two isolated Mg's from there 

119212—37 18 



264 



BULLETIN 169, UNITED STATES NATIONAL MUSEUM 



are closer to those from Loc. 25. This impression of slight heterogene- 
ity cannot now be considered dependable or formally recognized. 
The differences could hardly be of more than subspecific scope in any 
event and perhaps are merely those of separate strains within one 
subspecies, and the data are too few to establish them as real. 

The best data for material from one locality, dimensions of P4 and 
Ml from the Gidley Quarry, may be compared with the Torrejon 
sample by Fisher's t-test, previously mentioned, with the following 
results: 



Variate 


Ni-FNa 


t 


P 


LP4 


20 


2.22 


<0.05>0.02 


WP4 


20 


1.60 


<0.2>0.1 


LMi 


19 


2.83 


<0.02>0.01 


WMi 


19 


1.74 


<0.2>0.1 



Thus these two teeth are probably significantly longer, but not 
wider, than those of the Torrejon sample as a whole. Since the latter 
is heterogeneous in origin and perhaps as to race, it does not neces- 
sarily follow that the Gidley Quarry race does not occur in the Torre- 
jon, but it probably does not. Comparison of the whole Fort Union 
sample, however, shows no significant difference, as the following 
figures for the only variates probably significant in the Gidley Quarry 
sample show: 



Variate 


N, + N2 


t 


P 


LP4 


25 


1.95 


<0.1>0.05 


LM, 


22 


1.66 


<0.2>0.1 



In short, the evidence now is that the Fort Union sample may 
include more than one local or temporal genetic group of minor 
scope and the same may be true of the Torrejon material. At least 
one of these minor groups in the Fort Union is distinct from the 
Torrejon sample as a whole and probably from any group included in 
the latter. But the definitive separation of these minor groups can- 
not be accomplished from the data now available, and there is no 
significant dift'erence between the Fort Union Anisonchus as a whole 
and that of the Torrejon as a whole. All are referable to a single 
species, A. sectorius. 

Table 62. — Numerical data on P4 of Anisonchus sectorius 



Variate 


N 


R 


M 


a 


V 


LP4 

WP4 


25 
25 


5. 3-6. 6 
3. 5-4. 3 


5. 94 ±0.05 
3. 92 ±0.04 


0. 31±0. 04 
0.20 ±0.03 


5. 2±0. 7 
5. 2±0. 7 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 265 

As an indication of the variation of the whole species as thus known, 
data for P4, a rather variable and characteristic tooth best represented 
in the combined collections, are here presented (table 62). Individual 
measurements of the many specimens studied, and many other data, 
are on hand and will be permanently filed. 

The uniformity of these results with those based on Torrejon 
specimens only is striking. Despite the great increase (one and a 
half times) in the size of the sample by the addition of specimens of 
widely different provenience, the two means are increased by only 
0.08 and 0.04, respectively, the first figure only 0.01 more than the 
corresponding standard error for the smaller sample and the second 
less than the corresponding standard error. The standard de\dations 
are altered by amounts considerably less than their standard errors in 
the smaller sample and the same is true of one coefficient of variation, 
while the other is not changed at all. 

The interest of the coefficients of variation for the Torrejon sample 
should also be pointed out. One of them, for WP3 is unusually high, 
but this is largely caused by the single aberrant or abnormal specimen 
previously mentioned. ^^ If we accept P3 as abnormally variable or as 
represented by some extraneous material, the other eight coefficients 
of variation range from 3.8 to 5.7 and average 4.8.'^ The accumula- 
tion of such figures is of great importance in view of our almost com- 
plete lack of any exact knowledge of the variability of fossil species 
in samples collected under the usual field conditions. 

The preceding discussion is based on lower teeth. The upper 
dentitions have also all been examined and compared, but they merely 
substantiate the evidence of the lower dentitions, and the samples 
are less satisfactory in all respects. 

Order PANTODONTA Cope, 1873 (as suborder), new usage 

The order Dinocerata (emended from Dinocerea) was proposed for 
the uintatheres by Marsh in 1872, In 1873 Cope proposed to reduce 
this to subordinal rank and with the new suborder Pantodonta, for 
the coryphodonts, placed it in the order Proboscidea. In 1875 the 
two suborders were transferred by Cope to a new order Amblypoda. 
In 1883 he added to this order the suborder Taligrada, based solely 
on Pantolambda, and in 1897, as stated on an earfier page, added the 
periptychids to the Tahgrada. Marsh in 1884 proposed "Ambly- 
dactyla" and "Coryphodontia" as strict synonyms of Cope's names 
(which Marsh claimed to be essentially preoccupied) Amblypoda and 

« Omission of this specimen would reduce V from 12.3 to 7.5±2.0. 

'« This is within twice the standard error (that is, within the range of probable true values) for all the 
■single coefficients and is within less than the standard error for all but two. If the aberrant individual be 
omitted, it is also well within the range of probable true values for P3. 



266 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 

Pantodonta, respectively, but these names have not been generally 
accepted. 

The classification thus achieved is well summed up by Osborn (1898): 

Order Amblypoda: 

Suborder Taligrada: 

Periptychidae. 

Pantolambdidae. 
Suborder Pantodonta: 

Coryphodontidae. 
Suborder Dinocerata: 

Bathyopsidae. 

Uintatheriidae. 

This arrangement is now classic and with sUght modifications has 
since come into all but universal use. Nevertheless, in the hght of 
later discovery and research, it has little to recommend it. 

The probable affinities of the periptychids with the condylarths, 
rather than with the pantolambdids, have been discussed on a pre- 
vious page. On the other hand, all recent work (see especially Simp- 
son, 1929d, and Patterson, 1934) tends to emphasize the essential 
unity of Pantolambda and Coryphodon and their respective allies. 
The known pantolambdids are not ancestral to the known corypho- 
donts, and family separation is warranted, but they are so similar in 
structure aside from primitive or progressive features generally cor- 
related with greater or lesser age that there seems no reason to place 
them in separate suborders, and the distinction between Taligrada 
and Pantodonta is unwarranted. 

The uintatheres, on the contrary (Simpson, 1929d and elsewhere), 
seem to be a group independent of the pantolambdids and cory- 
phodonts from a very remote time and Hnked to them only through a 
prot- or perhaps even pre-ungulate, non-"amblypod" ancestry. The 
classic arrangement was undoubtedly influenced by the belief that 
taligrades, pantodonts, and dinoceratans represented oft'shoots of a 
single stock appearing successively in time with correspondingly 
progressive specializations. Now it is clear that this simple picture 
does not correspond to the facts. Among the supposed "taligrade" 
periptychids the more advanced members are the only ones that 
show any considerable resemblance to the pantolambdids in foot 
structure, but they cannot possibly be ancestral to the latter not only 
because they are contemporaneous but also because aside from the 
feet (and in part including them) their structure is very different. 
The idea of successive offshoots does apply to the pantolambdids and 
coryphodonts, but it decidedly breaks down again with the cory- 
phodonts and uintatheres because these groups are not successive but 
contemporary phyla, and it is the latest and most advanced members 
of each that show some resemblance, which hence is only convergent, 
and the earher members are even more decisively dissimilar. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 



267 



The classification seems, in fact, to have been based on grades of foot 
specialization, over the prototypal ungulate foot, rather than on 
characters peculiar to natural phyla. It thus united periptychids 
and pantolambdids because they had advanced relatively little in 
limb structure, even though their phyletic relations must have been 
distant. It separated (subordinally) pantolambdids and cory- 
phodonts because the former were less and the latter more advanced in 
limb specilization, despite the clear evidence that these groups are 
closely related phyletically. And finally it united coryphodonts and 
uintatheres because both have specialized limb structures, but over- 
looked their marked phyletic separation. 

The revision of nomenclature for the accurate representation of 
these newer points of view is difficult. The following diagram shows 
the relationships of the classic names to the groupings now considered 
natural : 





1 










Condylarthra. 












Amblypoda 








Taligrada 






, — • . 






As originally proposed. 


Pantodonta 










— ^ 


Dinocerata . 








Condylarthra 


• . 
















Amblypoda 


1 












Taligrada. 




' 


Cope and accepted by most 


Pantodonta 








• • 




other authors. 


Dinocerata . . 










■ ■ 












^ 










Condylarthra 








Pantodonta.. 










__ 




Dinocerata 


As here modified. 








S ^ 








13 














3 -^ 


















a 2 








g § 




















































ca 
























5^ 


a 


•a 


a 


■s ^ 






O (3 




.Q 










O 

§9 


^ 


a 


S3 


l« 






o - 


a, 


o 


P. 


s ^ 






as a 




a 


t-, 


a '- 






> " 














Ph 


(i( 


o 


t3 





Since both periptychines C'Catathlaeus") and anisonchines {Anison- 
chus) were explicitly cited among the genera belonging to the Con- 
dylarthra when that group was first proposed, since most definitions 
of Condylarthra need little or no alteration to include the periptychids, 
and since no other ordinal or subordinal name has been based primarily 
on the periptychids, the removal of the Periptychidae to the Condy- 
larthra raises no nomenclatural problem. 



268 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

The name Dinocerata was originally based on the uintatheres alone 
and has always been taken as referring to them and including only 
them,^^ so there can be no question as to the propriety of continuing 
this name in this usage. 

What remains is to settle on a name for the Pantolambdidae and 
Coryphodontidae. Some students (including me, 1931) have used 
"Amblypoda" essentially in this sense, usually including the Perip- 
tychidae. There is good precedent for such a restriction of a name to 
one of several groups formerly included in it, and it is generally more 
advisable than coining a new name. In the present case, however, it 
should be avoided if possible. "Amblypoda" was based about equally 
on the coryphodonts and the uintatheres. To exclude the uintatheres 
from it is not quite the removal of the type group but certainly is a 
radical change in usage and one not well justified. 

The name "Taligrada" might be expanded to this usage, but this 
also is objectionable. As originally defined it was carefully drawn so 
as to exclude and contrast with the best-known members of the group 
for which a name is now sought, that is, the coryphodonts. Further- 
more, in the past 40 years it has almost invariably been taken to 
include or even to be typified by the periptychids. 

"Pantodonta" has none of these objections. It was proposed and 
has always been used for typical members of the group now in question. 
No animals foreign to this group have ever been called pantodonts. 
Its original definition, although brief, offers a good contrast with both 
Condylarthra and Dinocerata, even as those groups are now under- 
stood, and would include the pantolambdids (not known when the 
name wa's proposed), so that we are using the name exactly in the 
sense of the original author, in fact more so than he did later. The 
fact that a group that he later excluded from the Pantodonta is now 
included seems to be of no particular importance, especially as his 
original conception is not thereby changed. It is entirely proper in 
taxonomy to extend a name formerly applied to one group to include 
another later found to be closely related and is open to much less 
question than would be the exclusion from a named group of a sub- 
division on which it was originally largely based (as in excluding 
uintatheres from the Amblypoda). The name "Amblypoda" I 
would discard altogether, as not pertaining to any group acceptable 
as natural or convenient in modern taxonomy. 

The present conception of the group Pantodonta may be summarized 
as follows: 



" Marsh did suggest synonymy with Cope's broader "Amblypoda", but in fact nothing but the uinta* 
theres was meant to be inchided in the original description and Marsh later (1S84) accepted this restriction, 
for he proposed "Amblydactyla" to replace "Amblypoda" and to include both coryphodonts and uin- 
tatheres, with only the latter listed as "Dinocerata." 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 269 

Order Pantodonta: A group of middle-sized to large, very archaic ungulates (or 
"subungulates"). The dentition is little or not reduced in number, and 
remains practically brachj'odont, but exhibits a high degree of lophiodonty 
even in the earliest members. The primitive pattern is strongly selenodont 
but this is secondarily masked to some extent in later forms. The canines 
are apparently always large, and may develop into great tusks. Skull and 
jaws are generally massive with verj^ powerful muscle attacliments. The 
brain remains very small and primitive. The limbs are massive and strong, 
ambulatory to graviportal, and retain many primitive features such as 
separate radius and ulna, tibia and fibula, and five toes on each foot. 
Carpus and tarsus retain and strongly accentuate the alternating arrange- 
ment. 
Family Pantolambdidae: Relatively less advanced forms, with the teeth 
fully selenodont, the skull roof little or not flattened, the tail long 
and heavy, and other primitive characters. 
Subfamily Pantolambdinae: Lighter, more ambulatory types of smaller 
size and with astragalus still retaining some condylarth characters. 
Middle Paleocene. North America. 
Subfamily Barylambdinae: Heavy graviportal types of larger size, with 
fuU}^ specialized pantodont type of astragalus. Upper Paleocene. 
North America. 
Family Coryphodontidae: Highly specialized forms, large in size, all with 
graviportal limbs, teeth with primitive crescents considerably modified, 
skull roof broad and flat, tail reduced. Upper Paleocene — lower Eocene 
in North America. Lower Eocene in Europe. Upper Eocene to Middle 
Oligocene in Mongolia. 
Family Pantolambdodontidae: A somewhat dubious group known from 
lower jaws only, which suggest relationship with Pantolambda but have 
numerous differences in details. Upper Eocene. Mongolia. 

The present fauna contains few remains of pantodonts, but Panto- 
lambda is represented by various fragmentary specimens, some of 
wliich indicate a species first defined, and at present known only, from 
this fauna. ^^ 

Family PANTOLAMBDIDAE Cope, 1853 

Genus PANTOLAMBDA Cope, 1883 

Douglass (1902b, p. 224) described and figured an upper premolar 
perhaps of this genus. It is about the size of P^ of P. bathmodon, but 
differs somewhat in form, the main cusp being more central and the 
external margin less sharply notched. The National Museum ma- 
terials does not serve to define this form. The second Pantolambda 
mentioned by Douglass (1908, p. 24) probably belongs to the species 
defined below. 



28 The present conception of the Pantodonta, especially as regards its essential unity as here defined, 
owes much to Patterson's discovery of complete skeletons oi Baryla mbda and to his fine studies of them (Pat- 
terson, 1933, 1934, 1935, 1937). Although not from the Crazy Mountain Field, the type species and specimen 
of Titanoide!^ was found in the Fort Union and named and described by Gidley (1917), and it was originally 
proposed to include a discussion of it in this work, but Patterson's studies make this quite unnecessary. 



270 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

PANTOLAMBDA INTERMEDIUS Simpson 

Figure 80 
Pantolamhda intermedius Simpson, 1935d, p. 244. 

Type. — U.S.N.M. No. 8384. Left lower jaw with Mi_2 and alveoli 
of C-P4, associated with symphysis fragment with right Ii_2 and 
alveoli of left I,_3. Collected by Dr. J. W. Gidley. 

Horizon and locality. — Gidley Quarry, Fort Union, Middle Paleocene 
horizon, Crazy Mountain Field, Mont. 




FiGDRE &Q.—Pantolambda inlermedius Simpson, U.S.N.M. no. 8384, right lower jaw: a, Crown view; b, 

external view. Natural size. 



Diagnosis. — Intermediate in size between P. bathmodon and P. 
caviridus. Pi with one large root, close to canine, followed by short 
diastema. P2_4 2-rooted. Lower molars closely resembling those of 
P. caviridus but entoconid more distinct. 

Discussion. — The type has Mi_2 somewhat corroded on the inner 
side. An isolated lower premolar, probably P2, no. 9598, from the 
same quarry as the type, is probably of this species. It is 2-rooted 
(as was P2 of the type) and is as long as Pg of P. caviridus but is con- 
siderably narrower and simpler. In P. caviridus the posterointernal 
crest from the main apex bifurcates and a sharp branch runs from it 
anterointernaUy, whereas in this tooth the posterointernal descending 
crest is less prominent throughout and has no bifurcation or antero- 
internal branch. The talonid is a narrow, simple heel. 

On the whole this species seems to resemble P. caviridus but is 
both smaller and more primitive structurally. Length Mi, 13.2; 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 271 

width All, 11.2; length M2, 14.8; width M2, 12.1; length P2 (referred) 
11.8; width P2 (referred), 6.8. (The widths may have been a Uttle 
greater before the teeth were corroded.) 

PANTOLAMBDA or allied genera, species nndetennined 

U.S.N.M. no. 6155 is an isolated M^ from "K mile N. of Fish Creek 
Creek 200 ft. E. of Melville and Harlowton Road", in Fort Union 
No. 3. This almost certainly means Loc. 28; it is about a half mile 
from Fish Creek, but no other mammal locality more nearly corre- 
sponds with the indication. This horizon is 400 feet above the base 
of No. 3 and about 550 feet above the Gidley Quarry. This tooth 
resembles the smaller Torrejon specimens referred to P. cavirictus 
but has the cingula, external and internal, better developed. 

No. 9858, from Loc. 18, well up in Fort Union No. 3, is a frag- 
ment of an upper molar probably of the same species as no. 6155. 

No. 9694, from Loc. 54, the same level as the Gidley Quarry, is a 
symphysis and isolated Mo, which also approach small P. cavirictus in 
size and is perhaps of this same species, although possibly still smaller. 
It is nearer P. cavirictus than P. intermedius in size. 

No. 10048, from the Gidley Quarry, closely resembles a lower 
posterior premolar of Pantolambda bathmodon in form but is smaller, 
7.3 mm long and 5.9 wide. 

All these specimens are inadequate for determination, but they 
show that pantolambdids were not uncommon in this general area 
and that they were varied, despite the fact that conditions did not 
lead to the good preservation of their remains. 

There are also isolated bones, without associated teeth, from the 
horizon of the Gidley Quarry and in one unimportant case, the base of 
No. 3, which probably belong to Pantolambda. AU are as large as the 
corresponding parts of Torrejon P. cavirictus and differ only in insig- 
nificant details. Since the probabilities suggest that some of these 
belong to P. intermedius, it may be that the latter was a small-headed 
form, with body equal to P. cavirictus in size but jaws and teeth con- 
siderably smaller. In the absence of associated material, however, 
this is obviously hypothetical. 



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fORT UNIOISr OF CRAZY MOUNTAIX FIELD, MONT. 273 

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the Amblypoda. Proc. Amer. Phil. Soc, vol. 73, pp. 71-101. 

1935. Second contribution to the osteology and affinities of the Paleocene 

amblypod Tiianoides. Proc. Amer. Phil. Soc, vol. 75, pp. 143-162, 
6 figs. 
1937. A new genus, Barylambda, for Titanoides faberi, Paleocene amblypod. 
Field Mus. Nat. Hist. Publ., geol. ser., vol. 6, no. 16, pp. 229-231. 
Eomer, Alfred Sherwood. 

1933. Vertebrate paleontology, 491 pp., 359 figs. Chicago. 
Russell, Loris Shano. 

1926. A new species of the genus Catopsalis Cope from the Paskapoo forma- 
tion of Alberta. Amer. Journ. Sci., vol. 12, pp. 230-234, 1 fig. 

1928. A new fossil fish from the Paskapoo beds of Alberta. Amer. Journ. 

Sci., vol. 15, pp. 103-107, 4 figs. 

1929. Paleocene vertebrates from Alberta. Amer. Journ. Sci., vol. 17, pp. 

162-178, 5 figs. 
1932a. New data on the Paleocene mammals of Alberta, Canada. Journ. 

Mamm., vol. 13, pp. 48-54. 
1932b. The Cretaceous-Tertiary transition of Alberta. Trans. Roy. Soc. 

Canada., sect. 4, ser. 3, vol. 26, pp. 121-156, 2 pis. 

1934. New fossil fresh-water Mollusca from the Cretaceous and Paleocene 

of Montana. Journ. Washington Acad. Sci., vol. 24, pp. 128-131, 
5 figs. 
Schlaikjer, Erich Maren. 

1933. Contributions to the stratigraphy and paleontology of the Goshen 

Hole area, Wyoming. I. A detailed study of the structure and 

relationships of a new zalambdodont insectivore from the middle 

Oligocene. Bull. Mus. Comp. Zool., vol. 76, pp. 3-27, 8 figs, 1 pi. 

Schlosser, Max. 

1923. Mammalia. In Karl von Zittel's Grundziige der Palaontologie, vol. 2, 
Vertebrata, pp. 402-689, figs. 505-800. Ed. 4. Miinchen and 
Berlin. 
Scott, William Berryman. 

1892. A revision of the North American Creodonta with notes on some 
genera which have been referred to that group. Proc. Acad. Nat. 
Sci. Philadelphia, 1892, pp. 291-323. 
1913. A history of land mammals in the Western Hemisphere, 693 pp., 304 
figs. New York. 
Simpson, George Gaylord. 

1926. Mesozoic Mammalia. IV. The multituberculates as living animals. 

Amer. Journ. Sci., vol. 11, pp. 228-250, 8 figs. 

1927. Mammalian fauna and correlation of the Paskapoo formation of 

Alberta. Amer. Mus. Nov., no. 268, 10 pp., 7 figs. 
1928a. A new mammalian fauna from tlie Fort Union of southern Montana. 
Amer. Mus. Nov., no. 297, 15 pp., 14 figs. 



276 BULLETIN 169, UNITED STATES NATIONAL MUSEUM 

Simpson, George Gaylord — Continued. 

1928b. Affinities of the Mongolian Cretaceous insectivores. Amer. Mus. 

Nov., no. 330, 11 pp., 1 fig. 
1928c. A catalogue of tlie Mesozoic Mammalia in the Geological Department 

of the British Museum, 215 pp., 55 figs., 12 pis. British Museum 

(Natural History), London. 
1929a. A collection of Paleocene mammals from Bear Creek, Montana. 

Ann. Carnegie Mus., vol. 19, pp. 115-122, 4 figs. 
1929b. Third contribution to the Fort Union fauna at Bear Creek, Montana. 

Amer. Mus. Nov., no. 345, 12 pp., 5 figs. 
1929c. Paleocene and lower Eocene mammals of Europe. Amer. Mus. Nov., 

no. 354, 17 pp. 
1929d. A new Paleocene uintathere and molar evolution in the Amblypoda. 

Amer. Mus. Nov., no. 387, 9 pp, 9 figs. 
1929e. American Mesozoic Mammalia. Mem. Peabody Mus., Yale Univ., 

vol. 3, pt. 1, 235 pp., 62 figs., 32 pis. 

1931. A new classification of mammals. Bull. Amer. Mus. Nat. Hist., vol. 

59, pp. 259-293. 

1932. A new Paleocene mammal from a deep well in Louisiana. Proc. U. S. 

Nat. Mus., vol. 82, art. 2, 4 pp., 1 fig. 

1933a. The "plagiaulacoid" type of mammalian dentition. A studj' of con- 
vergence. Journ. Maram., vol. 14, pp. 97-107. 

1933b. Glossary and correlation charts of North American Tertiary mammal- 
bearing formations. Bull. Amer. Mus. Nat. Hist., vol. 67, pp. 
79-121, 8 figs. 

1935a. The Tiffany fauna, upper Paleocene. I. — Multituberculata, Mar- 
supiaha, Insectivora, and ?Chiroptera. Amer. Mus. Nov., no. 795, 
19 pp., 6 figs. 

1935b. The Tiffany fauna, upper Paleocene. IL — Structure and relation- 
ships of Plesiadapis. Amer. Mus. Nov., no. 816, 30 pp., 11 figs. 

1935c. The Tiffany fauna, upper Paleocene. IIL — Primates, Carnivora, 
Condylarthra, and Amblypoda. Amer. Mus. Nov., no. 817, 28 
pp., 14 figs. 

1935d. New Paleocene mammals from the Fort Union of Montana. Proc. 
U. S. Nat. Mus., vol. 83, pp. 221-244. 

1936a. Data on the relationships of local and continental mammalian faunas. 
Journ. Pal., vol. 10, pp. 410-414, 2 figs. 

1936b. A new fauna from the Fort L^nion of Montana. Amer. Mus. Nov., 
no. 873, 27 pp., 16 figs. 
Simpson, George Gaylord, and Elftman, Herbert Oliver. 

1928. Hind limb musculature and habits of a Paleocene multituberculate. 
Amer. Mus. Nov., no. 333, 19 pp., 6 figs. 
Simpson, George Gaylord, and Roe, Anne. 

. The use of numerical data in zoology. (In press.) 

Sinclair, William John, and Granger, Walter. 

1911. Eocene and Oligocene of the Wind River and Bighorn basins. Bull. 

Amer. Mus. Nat. Hist., vol. 30, pp. 83-117, 4 figs., 6 pis. 

1912. Notes on the Tertiary deposits of the Bighorn basin. Bull. Amer. 

Mus. Nat. Hist., vol. 31, pp. 57-67, 2 figs., 2 pis. 
Stanton, Timothy William. 

1909. The age and stratigraphic relations of the "Ceratops beds" of Wyoming 

and Montana. Proc. Washington Acad. Sci., vol. 11, pp. 239-293. 
1914. Boundary between Cretaceous and Tertiary in North America as 

indicated by stratigraphy and invertebrate faunas. Bull. Geol. 

Soc. Amer., vol. 25, pp. 341-354. 



FORT UNION OF CRAZY MOUNTAIN FIELD, MONT. 277 

Stanton, Timothy William, and Hatcher, John Bell. 

1905. Geology and paleontology of the Judith River beds, with a chapter on 
the fossil plants by F. H. Knowlton. U. S. Geol. Surv. Bull. 257, 
174 pp., 19 pis. 
Stehlin, H. G. 

1916. Die Saugetiere des schweizerischen Eccaens, pt. 2. Abh. schweiz. pal. 
Ges., vol. 41, pp. 1,299-1,552, 82 figs., 2 pis. 
Stone, Ralph Walter. 

1909. Coal near Crazy Mountains, Mont. U. S. Geol. Surv. Bull. 341, pp. 

78-91, 1 pi. 
Stone, Ralph Walter, and Calvert, William R. 

1910. Stratigraphic relations of the Livingstone formation of Montana. 

Econ. Geol., vol. 6, pp. 551-557, 652-669, 741-764, 2 pis. 
Teilhard de Chardin, Pierre. 

1916, 1921. Les mammiferes de I'Eocene inferieur franQais et leurs gisements. 

Ann. Paleont., vol 10, pp. 171-176, 1916; vol. 11, pp. 1-lOS, 1921; 

42 figs., 8 pis. (Also with serial pagination 1-116.) 
Thom, William Taylor, Jr., and Dobbin, Carroll Edward. 

1924. Stratigraphy of Cretaceous-Eocene transition beds in eastern Montana 

and the Dakotas. Bull. Geol. Soc. Amer., vol. 35, pp. 481-505, 3 

figs., 3 pis. 
Weed, Walter Harvey. 

1893. The Laramie and the overl3-ing Livingston formation in Montana, 

with report on flora by F. H. Knowlton. U. S. Geol. Surv. Bull. 
105, 68 pp., 6 pis. 

1894. Livingston, Mont., folio. U. S. Geol. Surv. Geol. Atlas no. 1, [5] pp., 

4 maps. 
1896. The Fort Union formation. Amer. Geol., vol. 18, pp. 201-211. 
1899. Little Belt Mountains, Mont., folio. U. S. Geol. Surv. Geol. Atlas no, 

56, 11 pp., 4 maps. 
Wegemann, Carroll Harvey. 

1917. Wasatch fossils in so-called Fort Union beds of the Powder River 

basin, Wyo., and their bearing on the stratigraphy of the region. 
U. S. Geol. Surv. Prof. Paper 108d, pp. 57-60, 2 pis. 
WooLSEY, Lester Hood; Richards, Ralph Webster; and Lupton, Charles 
Thomas. 
1917. The Bull Mountain coal field, Mussellshell and Yellowstone Counties, 
Mont. U. S. Geol. Surv. Bull. 647, 218 pp., 36 pis. 
Wortman, Jacob Lawson. 

1901-1904. Studies of Eocene Mammalia in the Marsh collection, Peabody 
Museum. Amer. Journ Sci., vol. 11, pp. 333-348, 6 figs., 1 pi.; 
pp. 437-450, 11 figs., 1 pL; vol. 12, pp. 143-154, 13 figs.; pp. 193- 
206, 13 figs.; pp. 281-296, 1 fig., 1 pi.; pp. 377-382, 4 figs.; pp. 
421-432, 12 figs., 1 pi.; vol. 13, pp. 39-46, 4 figs.; pp 115-128, 
6 figs ; pp. 197-206, 12 figs.; pp. 433-448, 13 figs.; vol. 14, pp. 
17-23, 2 figs.; vol. 15, pp. 163-176, 5 figs.; pp. 399-414, 419-436; 
vol. 16, pp. 345-368, 15 figs.; vol. 17, pp. 23-33, 4 figs.; pp. 133- 
140, 11 figs.; pp. 203-214, 14 figs. (Also a separate edition in 2 
parts, paged serially 1-250, to which reference is made.) 



U. S. NATIONAL MUSEUM 



BULLETIN 169 PLATE 2 





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BULLETIN 169 PLATE 3 







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Fort Union Group. Crazy Mountain Field. Mont. 

FOR EXPLANATION OF PLATE SEE OPPOSITE PAGE. 



Plate 3 

1, Air view, looking approximately south, with Sec. 33, T. 6 N., R. 16 E., near the 

middle of the picture (prominent but small isolated timber butte in this 
section). The meandering watercourse is Widdecombe Creek and is 
developed on the nonresistant Upper Lebo (Fort Union No. 2), as are the 
other low sodded areas through the central part of the picture. The main 
timbered ridge across the photograph is the northwest side of Bear Butte. 
The broken area between the small outlying butte and the patch of timber 
(on Bear Butte) farthest to the left, just beyond the road, is Loc. 5, one of 
Douglass' two localities where mammals were first found in the Fort 
Union. Part of Lion Butte forms the skyline in the center and right parts 
of the picture. 

2, Air view of the east side of the north end of Bear Butte, looking approximately 

south in Sec. 34, T. 6 N., R. 16 E. The rimrock of Bear Butte, along the 
upper edge of the picture, is the basal Melville (No. 3) sandstone, and the 
rest of this area is all on the Upper Lebo (No. 2). The shale exposure in 
the coulee above the road in the upper left of the picture is Loc. 6, one of 
Douglass' discovery sites. 



Plate 4 

1, Air view of the Gidley Quarry and vicinity, looking slightly north of cast, tlie 

foreground in Sec. 23, T. 5 N., R. 15 E. The slope in the foreground, on 
which the quarry is visible, is on the Upper Lebo (No. 2), as is also the 
broad valley of the Widdecombe Creek in the upper left. The higher 
level in the upper and right parts of the picture, and along the horizon, is 
supported by the basal Melville (Fort Union No. 3) sandstone. It is 
typically marked by evergreen timber, but in the foreground this timber 
extends sparsely well down onto the Lebo, Init only on talus derived from 
the Melville. Bear Butte is dimly visible along the left part of the horizon, 
and a small corner of Lion Butte is seen in the upper right corner. Between 
these, small hills upheld by isolated patches of the Melville may be seen. 

2, Air view of the Gidley Quarry, a closer view, looking more to the north, of part 

of the foreground of fig. 1. The picture was taken in 1935 and shows an 
advanced stage in the American Museum quarrying operations. The 
approximate area covered by the LT. S. National Museum work (and since 
filled in) is indicated by dotted lines. The larger section (A of Silberling's 
notes) is on the far (north) side of the small coulee, and the smaller (B) 
on the near side. The original discovery was made in the coulee near the 
spot marked by the cross. 



U. S. NATIONAL MUSEUM 



BULLETIN 169 PLATE 4 





Fort Union Group. Crazy Mountain Field, Mont. 

FOR EXPLANATION OF PLATE SEE OPPOSITE PAGE. 



U. S. NATIONAL MUSEUM 



BULLETIN 169 PLATE 5 






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Fort Union Group, Crazy Mountain field. Mont. 

FOR explanation OF PLATE SEE OPPOSITE PAGE. 



Plate 5 

1, Air view, looking approximately west-northwest, the foreground in Sec. 4, T. 

5 N., R. 16 E. The small drainage basin in the foreground is on the Upper 
Lebo (Fort Union No. 2). The Silberling Quarry is in the upper part of 
the main right (northwest) branch of the coulee. The sparse timber marks 
the basal Melville (No. 3) sandstone and the top of Bear Butte, which here, 
near the middle of its length, is at its narrowest point. Beyond this is the 
valley of Widdecombe Creek, hidden by Bear Butte, and beyond this, dim 
in the photograph, rise low hills, without timlaer, developed on the Lower 
Lebo (No. 1) along the axis of the Widdecombe Creek anticline. 

2, Site of the Silberling Quarry, looking approximately north in Sec. 4, T. 5 N., 

R. 16 E. The two figures near the middle of the picture stand near the 
ends of the main section of the quarry. The slope is on the uppermost 
part of the Lebo (upper No. 2), but the basal Melville (No. 3) lies immedi- 
ately above, and numerous talus blocks from it are seen. The quarry is 
not discernible as such, since the picture was taken in 1932, 24 years after 
intensive work there. 



Plate 6 

1, Typical exposure of the Lower Melville sandstone, looking approximately north 

in Sec. 23, T. 5 N., R. 15 E. The valley in the upper right corner is on the 
Upper Lebo (No. 2), with low barren hills of the Lower Lebo (No. 1) 
beyond it. 

2, Shell limestone in the Melville at L(ic. 40, Sec. 29, T. 5 N., R. 15 E. Such beds 

characterize the middle part of the Melville, although the formation is 
predominantly of sandstone and shale. The invertebrate beds are gen- 
erally not so thick or so well exposed as they are at this locality. The 
apparent nodules are gastropod shells. 



U. S. NATIONAL MUSEUM 



BULLETIN 169 PLATE 6 



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BULLETIN 169 PLATE 7 



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Fort Union Primates. 
1, Palaechthonalticusph Gidley, part of right lower jaw with P2-M2, type (U.S.N.M. no. 9532), external 
^rf c'x?.. ^ Quarry; 2, Pawmoviys maturus Gidley, part of right lower jaw with P^-Ms, paratype 
(U b.N.M. no. 9.545), e.xternal view, Gidley Quarry; 2a, same, crown view; 3, P. maturus, part of 
right lower jaw with P4-M3, type (U.S.N.M. no. 9473), external view, Gidlev Quarrv Zn, same 
crown view. (All figures about four times natural size; after Gidley.) 



U.'S. NATIONAL MUSEUM 



BULLETIN 169 PLATE 8 







Fort Union primates. 

1, Pronothodectes matthewi Gidley, part of left lower jaw with P4-M3, paratype (U.S.N.M. no. 9531), external 
view, Gidley Quarry; 2, Paromomys maturus Gidley, part of right lower jaw with Pj-Ms, paratype 
(U.S.N.M. no. 9475), external view, Gidley Quarry; 2a, same, crown view; 3, P. maturus, part of 
left lower jaw with P4-M3, paratype (U.S.N.M. no. 9337), external view, Gidley Quarry. (All 
figures about four times natural size; after Gidley.) 



U. S. NATIONAL MUSEUM 




1 




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BULLETIN 169 PLATE 9 




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Fort Union Primates. 

FOR EXPLANATION OF PLATE SEE OPPOSITE PAGE. 



Plate 9 

1, Plesiadapis gidleyi (Matthew), left upper molar, U.S.N.M. no. 10765, crown 

view. From the Tiffanj- beds near Ignacio, Colo.; for comparison with 
Pronolhodedes. 

2, Pronothodecles mattheivi. Gidley, right P^-M-, type (U.S.N.M. no. 9547), crown 

view. Gidley Quarry. 

3, Plesiadapis gidleyi (Matthew), right P^, U.S.N.M. no. 10659, crown view. 

From the Tiffany beds near Ignacio, Colo.; for comparison with Prono- 
thodecles. 

4, Plesiadapis rex (Gidley), left lower molar, type (U.S.N.M. no. 9828), crown 

view. Gidley Quarry. 

5, Palaechthon aUicuspis Gidley, right M'--, paratype (U.S.N.M. no. 9550), 

crown view. Gidley Quarry. 

6, Palaechthon aUicuspis Gidley, right M'--, paratype (U.S.N.M. no. 9551), 

crown view. Gidley Quarry. 

7, Paromomys depressidevs Gidley, right P^-M^, type (U.S.N.M. no. 9546), 

crown view. Gidley Quarry. 

8, Undetermined, probably primate upper incisor, U.S.N.M. no. 10090, lingual 

view. Gidley Quarry. 

9, Undetermined, probably primate upj^er incisor, U.S.N.M. no. 10010, lingual 

view. Gidley Quarry. 

10, Undetermined, probably primate upper incisor, U.S.N.M. no. 9928, lingual 

view. Gidley Quarry. 

11, Vrohixhly Pronothodectes matthewi Gidley, upper incisor, U.S.N.M. no. 10005, 

lingual view. Gidley Quarry. 

12, Probably Pronothodecles matthewi Gidley, upper incisor, U.S.N.M. no. 10044, 

lingual view. Gidley Quarry. 

13, Undetermined lower incisor, possibly Plesiadapis rex, U.S.N.M. no. 9827, 

lateral view. Probably Loc. 13. 

14, Undetermined, possibly multituberculate lower incisor, U.S.N.M. no. 9552, 

lateral view. Gidley Quarry. 

15, Undetermined, pair of upper incisors, U.S.N.M. no. 9917, lingual view. 

Gidley Quarry. 

16, Plesiadapis gidleyi (Matthew), poorly preserved upper incisor, U.S.N.M. 

no. 10639, lingual view. From Tiifany beds, 5^2 miles east of Bayfield, 
Colo. 
(All figures aVjout four times natural size; after Gidley.) 



U. S NATIONAL MUSEUM 



BULLETIN 169 PLATE 10 




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Fort Union Primates. 

PaLenochtha minor (Qidley), part of right lower jaw with P4-M:), type (U.S.N.M. no. 9G39), external 
view; la, same, crown view; 2, Elphidotarsius florencae Gidley, part of left lower jaw with Pf-M:), 
type (U.S.N.M. no. 9411), external view; 2a, same, crown view; 3, Pronofhodecfes matthewi Gidley, 
part of left lower jaw with base of incisor, canine (?), Ps and Pt-Ms, U.S.N.M. no. 9332, e.xternal 
view; 3a, same, crown view. (All figures about four times natural size; nfter Gidley. All from 
Gidley Quarry.) 



INDEX 



(Principal references are given in boldface) 



Abel, O., 86, 115, 141, 165. 
absarokae, Didelphodus, 110. 
Absarokee, Mont., 27. 
Absarokius, 144, 145, 168. 
aceroides, Platanus, 19. 
Aemeodon, 106-111. 
acmeodontoides, Emperodon, 109. 
acolvtus, EUipsodon, 53, 225, 227, 233, 
234, 239. 

Mioclaenus, 225. 
acutus, Viverravus, 208, 209. 
Adam, Lake, Mont., 13, 23, 37. 
Adapinae, 148. 
Adapis, 148. 

admirabilis, Ptilodus, 84, 85. 
affinis, Sapindus, 19. 
agapetillus, Anisonchus, 225. 

Oxyacodon, 225, 227. 
Alder, 58. 

Allognathosuchiis, 59. 
Almagre formation, 196. 
alticuspis, Palaechthon, 33, 47, 62, 156 

seq., 159. 
Amblydactvla, 265, 268. 
Amblypoda, 217, 218, 265-268. 
amblyrhyncha, Populus, 57. 
American Fork, Mont., 13. 
American Fork formation, 14. 
americanus, Eucosmodon, 83, 104. 
americanus primus, Eucosmodon, 83, 

103, 104. 
Ampelopsis, 57, 58. 
Anacodon, 180, 195. 
Anaptomorphidae, 33, 60, 61, 142 seq. 
Anaptomorphus, 144. 
anceps, Plesiadapis, 35, 47, 50, 51, 156, 

168, 169. 
angustidens, Mimotricentes, 34, 36, 37, 

47-49, 52, 194, 197, 205 seq. 
Anisonchinae, 124, 217, 223, 224, 255 

seq. 
Anisonchus, 2, 50, 62, 216, 256, 258, 
262 seq., 267. 

agapetillus, 225. 

gillianus, 258, 259. 

mandibularis, 282. 

sectorius, 34, 37-41, 48, 50, 51, 53, 
54,255,259,261,262 seq. 
Apatemyidae, 147. 
Apatemys, 144. 
Apheliscidae, 124. 
Apheliscus, 124. 
Aphronorus, 106, 121, 124 seq. 

fraudator, 33, 38, 47, 53, 62, 124 
seq., 140. 
apiculatus, Oxyacodon, 225-227. 



119212—37- 



-19 



aquilonius, EUipsodon, 34, 37, 39, 47, 62, 

66, 227, 233, 234 seq., 238, 240. 
arachioides, Leguminosites, 57. 
Aralia notata, 57. 
Arbor-vitae, 58. 
Arctocyon, 171, 180. 

primaevus, 7. 
Arctocyonidae, 34, 60, 61, 170, 171 seq., 

207. 
Arctocyonides, 172. 
Arctocyoninae, 170-172, 173 seq. 
Arctoryctes, 139, 140. 
Artiodactyls, 220, 225, 229-231. 
asaphes, tJnuchiuia, 35, 47, 68. 
Aspideretes nassau, 59. 
australis, Thryptacodon, 42, 48, 68. 
Baldwin, D., 7, 233, 262. 
Barylambda, 11, 222, 269. 
Barylambdinae, 269. 
bathmodon, Pantolambda, 269-27L 
Bathvopsidae, 266, 267. 
Bats," 136. 
Bear Butte, Mont., 13, 16, 22, 23, 24, 28; 

31, 38. 
Bear Creek, Mont., 11, 170. 
Bear formation. 15, 17 seq., 21, 26-28, 

55, 57. 
Bearpaw formation, 15, 16. 
Bears, 180, 182. 
Beech, 58. 

belgicus, "Omomys", 144. 
Belt uplift, Mont., 14. 
Bessoecetor, 51, 52, 106, 121, 122 seq. 
diluculi, 33, 47, 122 seq. 
thomsoni, 35, 47, 50, 122, 123. 
Big Elk sandstone, 15. 
Bighorn Basin, Wj^o., 55, 83. 
Bighorn Mountains, Wyo., 11. 
Big Snowv Uplift, Mont., 14. 
Bigtimber, Mont., 12. 
Bigtimber Creek, Mont., 13. 
Billings County, N. Dak., 11. 
Birch, 58. 
Bittersweet, 58. 
Blainville, H. M. de, 7. 
Bolodon, 70. 
Bridger formation, 143. 
Broom, R., 71, 72, 86, 89-92. 
Brown, B., 11, 14. 
Buford, N. Dak., 7, 11. 
Bull Mountain Field, Mont., 26, 58. 
Burke, J. J., 6. 
Cabrera, A., 64, 246. 
Cabrera's Law, 64 seq. 
Caenolestes, 115. 
Caenolestidae, 136. 
Caenopithecus, 161. 

279 



280 



BULLETIN 169, UNITED STATES NATIONAL MUSEUM 



Calamodon, 169. 

Calvert, W. R., 9, 16, 19, 21, 22, 24, 26, 

27, 57. 
Campbell, M. R., 9, 57. 
Campeloma, 17, 58. 

limnaeiforme, 17. 

nebrascense whitei, 17. 
canadensis, Physa, 17. 
Carnivora, 34, 60, 61, 170 seq. 
Carpites, species undetermined, 57. 
Carpodaptes, 50, 51, 53, 161, 162, 164. 

hazelae, 35, 47. 
Carpolestes, 53, 144, 147, 161, 162, 164. 

dubius, 162. 
Carpolestidae, 33, 60, 61, 161 seq. 
Catathlaeus, 216, 267. 
cavirictus, Pantolambda, 41, 270, 271. 
Cayuse Butte, Mont., 8, 9, 13, 25, 29, 

35, 41. 
Champsosaurs, 17, 36, 59. 
Cheiromyoides, 165. 
Chestnut, 58. 
Chiroptera, 119, 135, 136. 
Chirox, 70. 
Choeroclaenus, 226, 228, 232 seq. 

turgidunculus, 226, 227. 
Chriacidae, 171, 172. 
Chriacinae, 172, 173. 
Chriacus, 52, 171-173, 192-194, 196 
seq., 198, 199, 201, 203, 258. 

pelvidens, 197. 

pugnax, 36, 47, 48, 194, 196, 197. 

pusillus, 194, 197-199. 

species undetermined, 35, 47. 
Chrysochlorid, 140. 
Cimolomys, 98. 

gracilis, 85. 
Claenodon, 2, 42, 50, 52-54, 62, 67, 173, 
174 seq., 190, 191, 195, 197, 224. 

corrugatus, 174-181. 

ferox, 39-42, 47, 49-51, 54, 55, 
174-179, 180 seq., 182-185, 189. 

latidens, 34, 47, 176, 187 seq., 190. 

montanensis, 34, 38, 47, 175, 176, 
181 seq., 187-189. 

procyonoides, 176. 

protogonioides, 175-177, 181, 186. 

Bilberlingi. 34, 42, 47, 176, 185 seq., 
188, 189. 

species undetermined, 34, 47, 189 
seq. 

species unnamed, 176, 178. 

vecordensis, 36, 47, 48, 176, 189. 
Claenodonts, 10. 
Claggett formation, 15. 
Clark Fork Basin, Wyo., 81, 83. 
Clark Fork formation, 11, 16, 20, 21, 81, 

83. 
Cloverley formation, 14. 
cochranensis, Ectypodus, 77, 82, 83, 

100, 1,01. 
Colorado group, 14, 15. 
comma, Conoryctes, 34, 39, 47, 53, 169. 
Conacodon, 256, 258. 

cophater, 258, 259. 

entoconus, 258. 



concordiarcensis, Prodiacodon, 33, 46, 

112 seq. 
Condylarthra, 34, 60, 61, 173, 216 seq., 

267, 268. 
Conoryctes, 50, 53, 169. 

comma, 34, 39, 47, 53, 169. 

species undetermined, 40, 47, 50. 
Conoryctidae, 169. 
Conoryctinae, 169. 
conus, Microcosmodon, 83. 
conventus, Neoliotomus, 83, 102. 
Cope, E. D., 7, 71, 127, 170, 176, 216- 

218, 224, 233, 246, 265, 267, 268. 
cophater, Conacodon, 258, 259. 
Coriphagus, 53, 173, 220, 256, 257 seq. 

encinensis, 259, 260. 

montanus, 9, 34, 48, 255, 257, 259, 
seq. 
corrugatus, Claenodon, 174-181. 
Coryphodon, 222, 223, 266. 
Coryphodontia, 265. 
Coryphodontidae, 266-269. 
Coryphodonts, 220, 265. 
Crazy Mountain Field, Mont., 14, 55. 
Crazy Mountain Syncline, Mont., 14. 
Crazy Mountains, Mont., 9, 12, 14, 22- 

26, 28. 
Crazy Peak, Mont., 12. 
Credneria daturaefolia, 57. 
Creodonta, 170 seq., 224. 
Crocodiles, 36, 59. 
cuneata, Populus, 57. 
cupanoides, Phyllites, 57. 
cuspidata, Eudaemonema, 33, 47, 131 

seq., 134. 
Cynodontomys, 128-130. 
Cypress, bald, 58. 
danae, Fusconaia, 17. 
daphnogenoides, Populus, 57. 
daturaefolia, Credneria, 57. 
dawkinsianus, Viverravus, 208. 
declivus, Nedionodus senectus, 59. 
Deltatheridiidae, 33, 60, 61, 107 seq., 

112. 
Deltatherium, 172, 192, 193. 
depressidens, Paromomys, 33, 47, 66, 

147, 154 seq., 157, 159, 164. 
Dermoptera, 131. 
Deuterogonodon, 53, 62, 173, 190 seq. 

montanus, 5, 37, 47, 49, 191, 192. 

species undetermined, 37, 47, 192. 
Diacodon, 111, 112, 117 
Dicliobunids, 230, 231. 
Didelphodontinae, 107 seq. 
Didelphodus, 106-111, 140, 258. 

absarokae, 110. 
Didymictis, 53, 67, 208, 209 seq., 214- 
216. 

haydenianus, 34, 37, 38, 47, 49, 
53, 209-211, 213. 

microlestes, 34, 37, 47, 62, 209, 210 
seq., 213. 

proteuus, 209, 210. 

tenuis, 34, 47, 210, 212 seq. 
diluculi, Bessoecetor, 33, 47, 122 seq. 

Palaeosinopa, 122. 



INDEX 



281 



Dinocerata, 265-268. 

Dinocerea, 265. 

Dinosaurs, 16, 17. 

disceptatrix, Haplaletes, 34, 48, 66, 226- 

228, 244 seq. 
disjunctus, Litaletes, 34, 37, 47, 66, 226, 

227, 234, 238, 239 seq. 
Dissacus, 53, 216. 
navajovius, 216. 

species undetermined, 34, 47, 216. 
dissentaneus, Litomylus, 34, 48, 66, 226, 

227, 241 seq. 
Djadochtatheriuna, 72. 
Dogs, 180, 208. 

Douglass, E., 6, 8, 9, 14-16, 21, 31, 38, 
52, 70, 104, 135-138, 169, 196, 250, 
257, 262, 269. 
douglassi, Ptilodus, 33, 46, 67, 74, 75, 

82, 83, 95, 96, 102. 
dubius, Carpolestes, 162. 
Eagle formation, 15. 
Earle, C, 7, 127, 171, 172, 217, 218, 

225, 258. 
Ectocion, 250-254. 

Ectypodus, 51, 52, 65, 67, 73, 81-83, 
99 seq. 
cochranensis, 77, 82, 83, 100, 101. 
grangeri, 33, 46, 67, 74, 75, 79, 82, 

83, 99, 101, 102. 
hunteri, 35, 46, 50. 
. musculus, 77, 79, 82, 83, 99, 101, 
102. 
russelli, 33, 46, 67, 74, 75, 79, 82, 

83, 99 seq. 
silberlingi, 33, 46, 67, 74, 75, 79, 

82, 83,97, 101 seq. 
species undetermined, 83, 102. 
elegans, Elpidophorus, 133. 
Elftman, H. O., 71, 92. 
EUipsodon, 53, 225, 227-232, 233 seq., 
238-240. 
acolytus, 53, 225, 227, 233, 234,239. 
aquilonius, 34, 37, 39, 47, 62, 66, 

227, 233, 234 seq., 238, 240. 
inaequidens, 225-227, 233, 236, 238, 

239 
lemuroides, 225, 227, 233, 234, 239. 
priscus, 227, 228. 
species undetermined, 41, 47, 238. 
Elliptio priscus, 17. 
EUis, A. J., 26. 
Elm, 58. 

Elphidotarsius, 50, 51, 53, 68, 147, 161, 
162 seq., 164. 
florencae, 33, 47, 68, 163 seq. 
Elpidophorus, 51, 53, 127, 129, 130, 
133 seq. 
elegans, 133. 

minor, 31, 33, 47, 49, 50, 133 seq. 
patratus, 35, 42, 47, 50, 51, 133. 
Emperodon, 107, 108. 

acmeodontoides, 109. 
encinensis, Coriphagus, 259, 260. 

Mixoclaenus, 257. 
entoconus, Conacodou, 258. 
Epanorthidae, 136. 



Erinaceidae, 106, 111. 
Eucosmodon, 52, 70, 72, 73, 76, 81-83, 
92, 103 seq. 
americanus, 83, 104. 
americanus primus, 83, 103, 104. 
gratus, 83, 104. 
molestus, 83, 104. 

sparsus, 33, 37, 46, 49, 83, 103 seq. 
teilhardi, 83, 104. 
Eudaemonema, 53, 106, 127, 129, 130, 
131 seq., 140. 
cuspidata, 33, 47, 131 seq., 134. 
Euprotogonia, 246, 250, 253. 
minor, 247, 253. 
puercensis, 247. 
subquadrata, 246. 
europaeus, Glyptostrobus, 57. 
europaeus ungeri, Glyptostrobus, 57. 
Eutheria, 72. 

excedens, Harpagosaurus, 59. 
Falconer, H., 71. 
Farr, M. S., 6, 8, 40. 
Ferns, 58. 

ferox, Claenodon, 39-42, 47, 49-51 , 54, 55 
174, 179, ISOseq., 182-185, 189. 
Mioclaenus, 224. 
Figs, 58. 

Fish Creek, Mont., 12, 28, 40, 41. 
Fish Creek beds, 16. 
Fisher, R. A., 2, 280, 264. 
Fishes 59. 

Fissipedia*, 170, 207, 208. 
Flora, 57 seq. 
florencae, Elphidotarsius, 33, 47, 68, 163 

seq. 
floverianus, Mioclaenus, 246. 
formosus, Halodon, 97. 
Ptilodus, 97, 101. 
Viviparus, 17. 
Fort Benton formation, 14. 
Fort Union group, 7, 15, 16, 20 seq. 
fossilis, Onoclea sensibilis, 57. 
Fox Hills formation, 16. 
fraudator, Aphronorus, 33, 38, 47, 53, 

62, 124 seq., 140. 
Friant, M., 229. 
Frontier formation, 15. 
frugivorus, Phenacolemur, 35, 47. 
furens, Prothryptacodon, 34, 38, 47, 194, 

195 seq. 
Fusconaia danae, 17. 
Gallegos Canyon, N. Mex., 233. 
Ganoids, 36. 
Gelastops, 52, 106, 107 seq., 140. 

parens, 33, 46, 109 seq. 
genetrix, Populus, 57. 
Germann, J. C, 6. 

Gidley, J. W., 3-6, 10, 21, 31, 32, 41, 52, 
56, 67, 70-72, 78, 86, 90-92, 97, 101, 
115-117, 141, 147-149, 154, 155, 159, 
166, 168, 174-176, 180-185, 187, 189- 
192, 194, 245-248, 250-253, 262, 269. 
Gidley Quarry Mont., 9, 10, 22, 30, 31 
seq., 35, 37-39, 46, 48-51, 55, 58 seq., 
68, 74-76, 93. 



282 



BULLETIN 169, UNITED STATES NATIONAL MUSEUM 



gidleyi, Nothodectes, 165. 

Plesiadapis, 16S. 

Ptilodus, 33, 38, 46, 67, 74, 75, 82, 
83, 95 seq. 
Gidleyina, 5, 39, 50, 51, 55, 246, 250 seq. 

montanensis, 5, 41, 48, 50, 251 seq., 
253 254. 

silberl'ingi, 40, 48, 50, 253 seq., 255. 

species undetermined, 41, 48, 50. 

superior, 42, 48, 254 seq. 
Giebel, C. Cx., 171. 
gillianus, Anisonchus, 258, 259. 
Gilmore, C. W., 4, 6, 59. 
Gingko, 58. 

Glass Lindsav Lakes, Mont., 13, 23, 28. 
Glendive, Mont., 57, 58. 
Glyptostrobus europaeus, 57. 

europaeus ungeri, 57. 
gracilis, Cimolomvs, 85. 

Ptilodus, 70, 74, 84. 
grandifoliolus, Sapindus, 19, 57. 
Granger, W., 7, 10, 11, 70-72, 92, 141, 

257. 
grangeri, Ectvpodus, 33, 46, 67, 74, 75, 

79, 82, 83, "99, 101, 102. 
Grasses, 58. 

gratus, Eucosmodon, 83, 104. 
Grav Bull formation, 16, 20, 21, 79, 81, 

83 
Gregory, W. K., 107, 148, 170. 
Grewia obovata, 57. 
Grewiopsis platanifolia, 57. 
Halodon formosus, 97. 

serratus, 101. 
Haplaletes, 51, 53, 226-230, 233, 241, 

243 seq. 

disceptatri.x, 34, 48, 66, 226-228, 

244 seq. 
Haploconus, 256, 258. 
Haplomvlus, 225-228, 230, 231, 241. 

speirianus, 226, 227. 
Hares, C. J., 11. 
Harlowton, Mont., 12, 40. 
Harpagosaurus excedens, 59. 
Hatcher, J. B., 16. 
Hav, O. P., 59, 257. 
Hayden, F. V., 7. 

havdenianus, Didymictis, 34, 37, 38, 47, 
49, 53, 209-211, 213. 
Didymictis (Protictis), 209. 
haydenii, Platanus, 57. 
hazelae, Carpodaptes, 35, 47. 
Hazelnut, 58. 
Hell Creek formation, 15-20, 26-28, 55, 

56. 
Hemiacodon, 145. 
Hemithlaeus, 221, 222, 256, 258. 
Hickory, 58. 
Horsetails, 58. 

Hunter, Mr. and Mrs. F., 10. 
hunteri, Ectypodus, 35, 46, 50. 
Hyopsodinae, 241. 
Hyopsodontid, aff. Haplaletes, 42, 48. 

genus undetermined, 221. 
Hvopsodontidae, 34, 60, 61, 66, 217, 

220, 222, 223, 224 seq. 



Hvopsodontids, 259. 

Hyopsodontinae, 223, 225, 231, 241 seq. 

Hyopsodus, 217, 223-226, 229-231. 

paulus, 226. 
Ictidopappus, 53, 208, 209, 213 seq. 

mustelinus, 34, 47, 214 seq. 
ignotus, Litolestes, 226, 227. 
inaequidens, Ellipsodon, 225-227, 233, 
236, 238, 239. 
Tricentes, 225. 
Indrodon, 127-130. 
Insectivora, 33, 60, 61, 104 seq., 217, 

218, 225, 229, 257. 
intermedins, Pantolambda, 34, 48, 270 

seq. 
Invertebrates, 58 seq. 
Jepsen, G. L., 6, 11, 20, 55, 79, 83, 120, 
141, 143, 147, 161, 162, 165, 225, 226, 
229. 
jepseni, Parectvpodus, 33, 46, 74, 75, 

82, 83, 100, 102 .seq. 
Judith River formation, 15-17. 
Kingsburv formation, 11. 
Klahn, H., 178. 

Knowlton, F. H., 9, 19-21, 56-58. 
Kootenai formation, 14, 15, 29. 
ladae, Leptacodon, 33, 46, 62, 113 seq., 

115. 
Lance formation, 15-21, 55-57. 
latidens, Claenodon, 34, 47, 176, 187 
seq., 190. 
Mimotricentes, 5, 34, 38, 47, 194, 

205, 206. 
Neoclaenodon, 187, 188. 
Tricentes, 194, 203, 205. 
latrunculus, Spanoxyodon, 34, 47, 68, 

194, 203. 
Laurels, 58. 

Lebo Creek, Mont., 8, 13, 22. 
Lebo formation, 9, 15, 16, 21 seq., 24-28, 

36, 37, 55, 57. 
Leguminosites arachioides, 57. 
Leipsanolestes, 113. 
Lemoine, V., 7. 

lemuroides, EUipsodon, 225, 227, 233, 
234, 239. 
Mioclaenus, 225. 
Lennep formation, 15, 16, 26. 
Lepisosteus species undetermined, 59. 
Leptacodon, 51, 52, 67, 106, 111, 112, 
113 seq., 117. 
ladae, 33, 46, 62, 113 seq., 115. 
munusculum, 33, 46, 114 seq. 
packi, 113, 114. 
siegfriedti, 113. 
tener, 35, 46, 50, 68, 113-115. 
Leptictidae, 33, 60, 61, 106, 107, 111 

seq., 120. 
limnaeiforme, Campeloma, 17. 
Lion Butte, Mont., 13, 24, 28. 
Lioplax nebrascensis, 59. 
Litaletes, 53, 226, 227, 231, 232, 238 
seq., 245. 
disjunctus, 34, 37, 47, 66, 226, 227, 
234, 238, 239 seq. 



INDEX 



283 



Litolestes, 51, 225-228, 241, 243. 
ignotus, 226, 227. 
notissimus, 3o, 48, 227. 
Litomvlus, 53, 226-228, 233, 241 seq., 
243, 245 
dissentaneus, 34, 48, 66, 226, 227, 
241 seq. 
Litotherium, 161. 

Livingston formation, 8, 9, 16, 19, 26, 27. 
Lizards, 59. 
Llovd, E. R., 11. 
Lobdell, J. F., 11. 
lobdelli, Psittacotherium, 170. 
Longnian, H. A., 115. 
Loxolophus, 171. 
Lull, R. S., 4. 
Lupton, C. T., 26, 58. 
lydekkerianus, Mioclaenus, 225. 
Magnolia, 58. 

mandibularis, Anisonchus, 262. 
Maple, 58. 

Marsh, O. C, 71, 217, 265, 268. 
Marsupials, 70-72, 115-117, 128. 
Matthew, W. D., 2, 7, 52, 64, 65, 70, 72, 
105, 107, 111, 115-120, 127-131, 140, 
141, 146, 169-177, 180, 194, 207, 209, 
216-219, 222, 223, 225-227, 230, 232, 
233, 246, 257, 258, 262. 
matthewi, Pronothodectes, 33, 47, 165 

seq. 
maturus, Paromomvs, 33, 39, 47, 62, 66, 

147, 149 seq., 154-157. 
mediaevus, Ptilodus, 52, 67, 70, 77-80, 

82, 83, 85, 96. 
Meek, F. B., 7. 
Megopterna, 135, 136. 

minuta, 9, 136-139. 
Meinzer, O. E., 26. 
Melville, Mont., 12, 14, 25, 40. 
Melville formation, 15, 20, 21, 25, 27, 

28, 39, 55. 
Meniscotheriidae, 216-218, 224. 
Meniscotheriinae, 224. 
Mesonvchidae, 34, 60, 61, 170, 216. 
Metachriacus, 53, 66, 172, 173, 192-194, 
196, 197 seq. 
provocator, 37, 38, 47, 49, 66, 194, 

200 seq., 204. 
punitor, 34, 47, 49, 62, 66, 194, 197 

seq., 201, 202, 204. 
species undetermined, 37, 47. 
Metatheria, 72. 

Miacidae,34,60,61, 170, 171, 182, 207 seq. 
Miacinae, 207, 208. 
Microclioerus, 144, 145. 
Microcosmodon, 73, 81. 

conus, 83. 
microlestes, Didymictis, 34, 37, 47, 62, 

209, 210 seq., 213. 
Microsyopinae, 128, 129. 
Microsvops, 127-130. 
Mimotricentes, 52, 53, 173, 192, 193, 
203 seq. 
angustidens, 34, 36, 37, 47-49, 52, 
194, 197, 205 seq. 



Mimotricentes latidens, 5, 34, 38, 47, 194, 
205, 206. 
species undetermined, 36, 47, 48, 
207. 
minor, Elpidophorus, 31, 33, 47, 49, 50, 
133 seq. 
Euprotogonia, 247, 253. 
Palaechthon, 159. 
Palenochtha, 33, 47, 159 seq. 
Tetraclaenodon, 249. 
minuta, Megopterna, 9, 136-139. 
Mioclaenidae, 217, 218, 225, 231, 232, 

257. 
Mioclaeninae, 218, 223, 225, 232 seq., 

257, 258. 
Mioclaenus, 5, 216, 217, 224-228, 230- 
233. 
acolytus, 225. 
ferox, 224. 
fioverianus, 246. 
lemuroides, 225. 
lydekkerianus, 225. 
opisthacus, 225. 
turgidunculus, 225, 232. 
turgidus, 224-227, 230, 232. 
Mixoclaenus, 173, 255, 257, 258. 

encinensis, 257. 
Mixodectes, 5, 53, 70, 127-131, 133. 
Mixodectidae, 33, 60, 61, 106, 127 seq. 
Mixodectinae, 128, 129. 
molestus, Eucosmodon, 83, 104. 
Monotremes, 71, 72, 92. 
montanensis, Claenodon, 34, 38, 47, 175, 
176, 181 seq., 187-189. 
Gidleyina, 5, 41, 48, 50, 251 seq., 

253, 254. 
Mvrmecoboides, 33, 47, 117 seq. 
Neoclaenodon, 174-176, 181, 188. 
montanus, Coriphagus, 9, 34, 48, 255, 
257, 259 seq. 
Deuterogonodon, 5, 37, 47, 49, 191, 

194. 
Ptilodus, 9, 33, 37, 38, 46, 52, 62, 
67, 70, 74-80, 82, 83, 84 seq., 
95-97. 
Mowry formation, 15. 
multifragum, Psittacotherium, 34, 47, 

49, 53, 68, 169 seq. 
Multituberculata, 2, 33, 60, 61, 70 seq. 
Multituberculate undetermined, 42. 
munusculum, Leptacodon, 33, 46, 114 

seq. 
musculus, Ectypodus, 77, 79, 82, 83, 99, 

101, 102. 
Musselshell River, Mont., 12, 14. 
mustelinus, Ictidopappus, 34, 47, 214 

seq. 
Myrmecobiidae, 115. 
Myrmecobius, 115, 116. 
MyrmecoVioides, 10, 52, 106, 111, 112, 
115 seq. 
montanensis, 33, 47, 117 seq. 
Nannopithex, 145. 
nassau, Aspideretes, 59. 
navajovius, Dissacus, 216. 
nebrascense whitei, CamjDeloma, 17. 



284 



BULLETIX 16 9, UNITED STATES NATIONAL MUSEUM 



nebrascensis, Lioplax, 59. 
Necrolemur, 144-146, 148. 
Nedionodus senectus, 17, 59. 

senectus declivus, 59. 
Neoclaenodon, 173-176. 

latidens, 187, 188. 

montanensis, 174-176, 181, 188. 

silberlingi, 175, 185. 
Neoliotomus, 81. 

conventus, 83, 102. 

ultimus, 83. 
Niobrara formation, 15. 
nobilis, Platanus, 58. 
notata, Aralia, 57. 
Notharctinae, 147. 
Notharctus, 217. 
Nothodectes, 141, 164, 165. 

gidleyi, 165. 
notissimus, Litolestes, 35, 48, 227. 
Nyctitheriidae, 33, 60, 61, 106, 118 seq. 
Nvctitherium, 119. 
Oak, 58. 

obovata, Grewia, 57. 
Omomys, 143, 161. 

belgicus, 144. 

vespertiniis, 144, 162. 
Onoclea, 58. 

sensibilis fossilis, 57. 
opisthacus, Mioclaenus, 225. 

Protoselene, 225-227. 
Ornithorhynchus, 71. 
Osborn, H. F., 7, 21, 71, 86, 127, 170- 

172, 217-219,225,258,266. 
Osgood, W. H., 115. 
Otter Creek, Mont., 13. 
Owen, E,., 71. 
Oxyacodon, 225-230, 232, 233. 241, 243. 

agapetillus, 225, 227. 

apiculatus, 225-227. 

priscilla, 225, 227. 

turgidunculus, 225. 
Oxyclaenidae, 171, 257, 258. 
Oxyclaeninae, 170-173, 192 seq. 
Oxyclaenus, 171, 172, 195. 
packi, Leptacodon. 113, 114. 
Palaechthon, 53, 142-145, 147, 148, 156 
seq., 159, 160, 164. 

alticuspis, 33, 47, 62, 156 seq., 159. 

minor, 159. 
Palaeosinopa, 52, 120-122, 124, 126, 
140, 258. 

diluculi, 122. 

species undetermined, 35, 47. 
Palenochtha, 53, 142-145, 148, 158 seq. 

minor, 33, 47, 159 seq. 
paleocena, Zaiiycteris, 136. 
Palm, 58. 

Pantodonta, 34, 60, 61, 265 seq. 
Pantolambda, 11, 27, 53, 221, 222, 265, 
266, 269 seq. 

bathmodon, 269-271. 

cavirictus, 41,270, 271. 

intermedins, 34, 48, 270 seq. 

species undetermined, 34, 39, 48, 
271. 



Pantolambdidae, 34, 60, 61, 217, 219, 

266-268, 269 seq. 
Pantolambdids, 35, 40, 41, 48, 49, 50» 

62, 218-220. 
Pantolambdinae, 269. 
Pantolambdodontidae, 269. 
Pantolestes, 120, 121, 140. 
Pantolestidae, 33, 60, 61, 106, 120 seq. 
Pantolestinae, 121 seq., 124. 
parens, Gelastops, 33, 46, 109 seq. 
Parectypodus, 52, 81-83, 99, 100, 102 
seq. 

jepseni, 33, 46, 74, 75, 82, 83, 100, 
102 seq. 

simpsoni, 77, 79, 82, 83, 102. 

species undetermined, 83. 

tardus, 77, 79, 83, 97, 103. 
Paromomys, 50, 51, 53, 63, 66, 67, 
142-147, 148 seq., 156, 157, 159, 
162, 164. 

depressidens, 33, 47, 66, 147, 154 
seq., 157, 159, 164. 

maturus, 33, 39, 47, 62, 66, 147, 
149 seq., 154-157. 
Paromomys, of., genus and species unde- 
termined, 42, 47, 156. 
Paskapoo formation, 11, 81, 83, 130. 
patratus, Elpidophorus, 35, 42, 47, 50, 

51, 133. 
Patterson, B., 11, 222, 266, 269. 
paulus, Hyopsodus, 226. 
Pearson, H., 78. 

Peltosaurus, species undetermined, 59. 
pelvidens, Chriacus, 197. 
Pelycodus, 148, 156, 162, 217. 
Pentacodon, 53, 106, 120, 121, 124, 126. 
Pentacodontinae, 121, 123 seq. 
Periptvchidae, 34, 60, 61, 216, 217, 219, 

220,^224, 255 seq., 266-268. 
Periptychinae, 217, 223, 224. 
Periptychines, 259. 
Periptychus, 62, 216, 218, 221, 222. 
Perissodactyla, 216. 
Phenacodaptes, 225, 226, 229-231. 

sabulosus, 226. 
Phenacodontidae, 34, 60, 61, 216-218, 

223, 245 seq. 
Phenacodonts, 62. 

Phenacodus, 54, 190, 191, 216, 223, 251. 
Phenacolemur, 50, 146, 147. 

frugivorus, 35, 47. 
Phenacops, 107, HI. 
Phyllites cupanoides, 57. 
PhvUostomatidae, 134, 135. 
Physa, 17. 

canadensis, 17. 
Picrodontidae. 33, 60, 61, 134 seq. 
Picrodus, 53, 107, 134, 135 seq. 

silberlingi, 9, 3-3-, 47, 136 seq. 
Pines, 58. 
Plagiaulax, 70. 
Plagiomene, 130. 
Plagiomenidae, 130, 257. 
planolatere, Viviparus, 59. 
Plants, 56. 



INDEX 



285 



platanifolia, Grewiopsis, 57. 
Platanus aceroides, 19. 

haydenii, 57. 

nobilis, 58. 

raynoldsii, 19. 

species undetermined, 19. 
Plateau Valley formation, 11. 
Platychoerops, 164. 
Plesiadapidae, 33, 60, 61, 143, 164 seq. 
Plesiadapis, 50, 51, 53, 141, 144, 147, 
164-166, 167 seq. 

anceps, 35, 47, 50, 51, 156, 168, 169. 

gidlevi, 168. 

rex, 42, 47, 51, 156, 167 seq. 

tricuspidens, 165. 
Plesiolestes, 141, 143, 165. 
Pleuraspidotheriidae, 218. 
Pleuraspidotheriinae, 224. 
pliciferus, Tetraclaenodon, 246-249, 253. 
Polecat Bench, Wye, 20, 27. 
politus, Viverravus, 208. 
Poplars, 58. 
Populus amblyrhyncha, 57. 

cuneata, 57. 

daphnogenoides, 57. 

genetrix, 57. 

species undetermined, 57. 
Porcupine Butte, Mont., 13, 25, 29, 41, 

42. 57. 
Potter Creek, Mont., 27. 
Powder River Basin, Wyo., 11. 
Prentice, S., 6. 
primaevus, Arctocyon, 7. 

Titanoides, 11. 
Primates, 2, 10, 33, 60, 61, 127, 128, 

135, 141 seq., 217. 
primus, Eucosmodon americanus, 83, 

103, 104. 
Princeton localities, Mont., 40, 46. 
Princeton Quarry, Wyo., 55. 
priscilla, Oxj^acodon, 225, 227. 
priscus, Ellipsodon, 227, 228. 

Elliptio, 17. 
Proboscidea, 265. 
procyonoides, Claenodon, 176. 
Prodiacodon, 52, 106, 107, 111, 112 seq. 

concordiarcensis, 33, 46, 112 seq. 

puercensis, 112, 113. 
Proectocion, 250. 
Proglires, 127. 

Pronothodectes, 50, 51, 53, 147, 162, 
164, 165 seq. 

matthewi, 33, 47, 165 seq. 
Proscalops, 140. 
protenus, Didymictis, 209, 210. 
Prothryptacodon, 51, 53, 173, 192, 193, 
194 seq., 199. 

furens, 34, 38, 47, 194, 195 seq. 
Protictis, 209. 

haj'denianus, 209. 
Protochriacus, 171. 
Protogonia, 216, 246. 

subquadrata, 246. 
protogonioides, Claenodon, 175-177, 
181, 186. 



Protogonodon, 5, 53, 172, 190, 191, 250, 

251. 
Protoselene, 225-232, 241, 251, 254. 

opisthacus, 225-227. 
provocator, Metachriacus, 37, 38, 47, 

49, 66, 194, 200 seq., 204. 
Pseudoloris, 161. 
Psittacotheriinae, 169 seq. 
Psittacotherium, 31, 53, 169 seq. 
lobdelli, 170. 

multifragum, 34, 47, 49, 53, 68, 169 
seq. 
Pterospermites, 57. 
Ptilodontid undetermined, 35. 
Ptilodontidae, 33, 60, 61, 73, 74, 80 seq. 
Ptilodus, 10, 31, 52, 65, 67, 70-73, 81-83, 
84 seq., 99, 161. 
admirabilis, 84, 85. 
douglassi, 33, 46, 67, 74, 75, 82, 83, 

95, 96, 102. 
formosus, 97, 101. 
gidlevi, 33, 38, 46, 67, 74, 75, 82, 

83, 95 seq. 
gracilis, 70, 74, 84. 
mediaevus, 52, 67, 70, 77-80, 82, 

83, 85, 96. 
montanus, 9, 33, 37, 38, 46, 52, 62, 
67, 70, 74-80, 82, 83, 84 seq., 
95-97. 

sinclairi,' 33, 36, 46, 48, 52, 62, 67, 
74-76, 78, 79, 82, 83, 96, 97 seq., 
101. 
species undetermined, 33, 46, 83. 
trovessartianus, 77, 82, 83, 96. 
puercensis, Euprotogonia, 247. 
Prodiacodon, 112, 113. 
Tetraclaenodon, 34, 39, 48, 49, 
246-248, 249 seq. 
Puerco formation, 7, 11, 16, 18, 21, 46, 
52-55, 81, 83, 173, 186, 191, 196, 224, 
255 259. 
Puet Creek, Mont., 28. 
pugnax, Chriacus, 36, 47, 48, 194, 196, 

197. 
punitor, Metachriacus, 34, 47, 49, 62, 

66, 194, 197 seq., 201, 202, 204. 
pusillus, Chriacus, 194, 197-199. 
raynoldsii, Platanus, 19. 
Red Lodge, Mont., 27. 
Reed Point, Mont., 27. 
Reptiles, 59, 
retusus, Viviparus, 59. 
rex, Plesiadapis, 42, 47, 51, 156, 167 seq. 

Tetonius, 167, 168. 
Richards, R. W., 26, 58. 
Rodents, 127, 128. 
Roger, O., 232. 
Romer, A. S., 86. 

Russell, L. S., 11, 17, 52, 58, 59, 101. 
russelli, Ectvpodus, 33, 46, 67, 74, 75, 

79, 82, 83i^ 99 seq. 
sabulosus, Phenacodaptes, 226. 
Sahx, species undetermined, 57. 
San Juan Basin, N. Mex., 2, 7, 55, 83, 
224. 



286 



BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



Sand Coulee formation, 16, 81, 83. 
Sapindus affinis, 19. 

grandifoliolus, 19, 57. 
species undetermined, 19. 
Scalops, 139. 
Scarritt Quarrv, Mont., 10, 25, 30, 34 

seq., 39, 41, 46, 50, 51, 54, 55, 60, 

61, 63. 
Schlaikjer, E. M., 139, 140. 
Schlosser, M., 86, 115, 120, 217, 224, 

257. 
Scott, W. B., 86, 216, 217, 224, 225, 246. 
sectorius, Anisonchus, 34, 37-41, 48, 50, 

51, 53, 54, 255, 259, 261, 262 seq. 
Sedges, 58. 
Selaginella, 68. 
senectus, Nedionodus, 17, 59. 
senectiis declivus, Nedionodus, 59. 
sensibilis fossilis, Onoclea, 57. 
Sentinel Butte formation, 25. 
Sequoias, 58. 
serratus, Halodon, 101. 

Ptilodus, 101. 
Shields River, Mont., 27. 
Shoshonius, 127, 145. 
siegfriedti, Leptacodon, 113. 
Silberling, A. C, 3, 4, 6, 8-10, 17, 18, 

21-23,^ 26, 27, 30-32, 34, 38, 40-42, 

56, 70, 86, 98, 133, 168, 250, 251, 257. 
Silberling Quarrv, Mont., 9, 10, 29, 30, 

31, 33 seq., 37, 39, 46, 48-51, 55, 56, 

59-62, 68, 74, 75, 93. 
silberlingi, Claenodon, 34, 42, 47, 176, 
185 seq., 188, 189. 
Ectvpodus, 33, 46, 67, 74, 75, 79, 

82, 83, 97, 101 seq. 
Gidleyina, 40, 48, 50, 253 seq., 255. 
Neoclaenodon, 175, 185. 
Picrodus, 9, 33, 47, 136 seq. 
-simplicidens, Stilpnodon, 33, 47, 52, 

68, 119, 120, 140. 
Simpson, G. G., 7, 54, 70, 71, 92, 107, 

120, 121, 136, 161, 194, 225, 266. 
simpsoni, Parectvpodus, 77, 79, 82, 83, 

102. 
Sinclair, W. J., 6, 7, 11. 
sinclairi, Ptilodus, 33, 36, 46, 48, 52, 62, 

67, 74-76, 78, 79, 82, 83, 96, 97 seq., 

101. 
Soricoidea, 104, 119. 
Spanoxvodon, 53, 173, 192-194, 203. 
latrunculus, 34, 47, 68, 194, 203. 
sparsus, Eucosmodon, 33, 37, 46, 49, 83, 

103 seq. 
speirianus, Haplomvlus, 226, 227. 
Stanton, T. W., 3, 9, 16, 18, 21-23, 57. 
Stehlin, H. G., 145, 146. 
Stillwater River, Mont., 27. 
Stilpnodon, 52, 119 seq. 

simplicidens, 33, 47, 52, 68, 119, 
120, 140. 
Stone, R. W., 9, 16, 19, 21, 22, 24, 26, 27, 

57. 
Stvlinodontidae, 34, 60, 61, 169 seq. 



Stylomyleodon, 59. 
subquadrata, Euprotogonia, 246. 

Protogonia, 246. 
superior, Gidleyina, 42, 48, 254 seq. 

Tetraclaenodon, 254. 
Sweetgrass Countv, Mont., 12, 14. 
Sweetgrass Creek,' Mont., 13, 41, 57. 
Sycamores, 58. 

svmbolicus, Tetraclaenodon, 5, 34, 36, 
^ 37, 39, 43, 48, 49, 246 seq., 249, 255. 
Taeniodonta, 34, 60, 61, 189 seq. 
Taeniolabis, 71, 90. 
Taligrada, 217-219, 265-268. 
Talpid, 140. 
Talpoidea, 104, 119. 
tardus, Parectvpodus, 77, 79, 83, 97, 103. 
Tarsioids, 144, 145, 148. 
Tarsius, 144, 146. 

Teilhard de Chardin, P., 7, 143, 165. 
teilhardi, Eucosmodon. 83, 104. 
tener, Leptacodon, 35, 46, 50, 68, 113- 

115. 
tenuis, Didvmictis, 34, 47, 210, 212 seq . 
Tetonius, 127, 144-146, 148, 168. 

rex, 167, 168. 
Tetraclaenodon, 5, 11, 39, 41, 43, 50-54, 
190, 191, 216, 221-223, 246 seq., 
251-255. 

minor, 249. 

pliciferus, 246-249, 253. 

puercensis, 34, 39, 48, 49, 246-248, 
249 seq., 250. 

species undetermined, 35, 42, 48, 
250. 

superior, 254. 

symbolicus, 5, 34, 36, 37, 39. 43, 
48, 49, 246 seq., 249, 255. 
Theria, 72, 92. 
Thermopolis formation, 15. 
Thomson, A. C, 10. 
thomsoni, Bessoecetor, 35, 47, 50, 122, 123. 
Thrvptacodon, 51, 53, 172, 173, 194, 195. 

'australis, 42, 48, 68. 
Tiffany formation, 7, 11, 20, 54, 55, 81, 

83, 112, 136, 141, 161. 
Tilia weedii, 57. 
Titanoides, 269. 

primaevus, 11. 
Tongue River formation, 25. 
Torrejon formation, 7, 11, 40, 52-55, 62, 
70, 74, 81, 83, 121, 128, 169-171, 173, 
175, 176, 178, 180, 181, 185-187, 189, 
196, 208-210, 213, 216, 224, 246-249, 
255, 257, 262-265, 271. 
Tricentes, 5, 11, 53, 171, 172, 192-194, 
197, 203-205. 

inaequidens, 225. 

latidens, 194, 203, 205. 
tricuspidens, Plesiadapis,165. 
Triisodon, 171. 
Triisodontidae, 171. 
Triisodontinae, 170, 172. 
Tritylodon, 71. 
trochiformis, Viviparus,17. 
Trogolemur, 146, 147. 



INDEX 



287 



trovessartianus, Ptilodus, 77, 82, 83, 96. 

Tullock formation, 20. 

turgidunculus, Choeroclaeiius, 226, 227. 

Mioclaenus, 225, 232. 

Oxyacodon, 225. 
turgidus, Mioclaenus, 224-227, 230, 232. 
Turtles, 17, 59. 
Uintalestes, 146, 147. 
Uintatheres, 265, 266, 268. 
Uintatheriidae, 266, 267. 
ultimus, Neoliotomus, 83. 
ungeri, Glvptostrobus europaeus, 57. 
Unio, 58. 

Unuchinia asaphes, 35, 47, 68. 
Ursidae, 182. 
Ursus, 185. 
vecordensis, Claenodon, 36, 47, 48, 176, 

189. 
vespertinus, Omomys, 144, 162. 
Viburnums, 58. 
Vitis xantholithensis, 57. 
Viverravidae, 208. 
Viverravinae, 170, 207, 208 seq. 
Viverravus, 53, 208, 209, 214, 216. 

acutus, 208, 209. 

dawkinsianus, 208. 

politus, 208. 



Viviparus, 17, 58. 

formosus, 17. 

planolatere, 59. 

retusus, 59. 

trochiformis, 17. 
Walnut, 58. 

Walvoord, Lake, Mont., 13, 23. 
Wasatch formation, 20, 21. 
Washakius, 145. 
Weber, R., 6. 
Weed, W. H., 8, 57. 
weedii, Tilia, 57. 
Wegemann, C. H., 11. 
Wetmore, A., 4, 6. 
Wheatland County, Mont., 12. 
whitei, Campeloma nebrascense, 17. 
Widdecombe Creek, Mont., 23, 28, 31^ 

36, 38. 
Wildcat Creek, Mont., 37. 
Wilmarth, M. G., 20. 
W^oolsey, L. H., 26, 58. 
Wortman, J. L., 7, 127, 170, 217. 
xantholithensis, Vitis, 57. 
Xenacodon, 111, 112. 
Yellowstone River, Mont., 12, 14, 27. 
Yew, 58. 
Zanycteris, 53, 134, 136. 

paleocena, 136. 



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